Adaptive doppler-nulling digitization for high-resolution

ABSTRACT

A system includes a transmitter node and a receiver node. Each node of the transmitter node and the receiver node are time synchronized to apply Doppler corrections associated with said node&#39;s own motions relative to a stationary common inertial reference frame. The stationary common inertial reference frame is known to the transmitter node and the receiver node prior to the transmitter node transmitting a plurality of signals to the receiver node and prior to the receiver node receiving the plurality of signals from the transmitter node. The receiver node performs adaptive digitization of the signals to account for a speed of the platform.

CROSS-REFERENCE TO RELATED APPLICATIONS

The present application is related to and claims the benefit of theearliest available effective filing dates under 35 USC § 120 as acontinuation in part of the following U.S. patent applications:

-   -   (a) U.S. patent application Ser. No. 17/233,107, filed Apr. 16,        2021, which is incorporated by reference in its entirety;    -   (b) P.C.T. Patent Application No. PCT/US22/24653, filed Apr. 13,        2022, which claims priority to U.S. patent application Ser. No.        17/233,107, filed Apr. 16, 2021, all of which are incorporated        by reference in its entirety;    -   (c) U.S. patent application Ser. No. 17/408,156, filed Aug. 20,        2021, which claims priority to U.S. patent application Ser. No.        17/233,107, filed Apr. 16, 2021, all of which are incorporated        by reference in its entirety;    -   (d) U.S. patent application Ser. No. 17/541,703, filed Dec. 3,        2021, which is incorporated by reference in its entirety, which        claims priority to:        -   U.S. patent application Ser. No. 17/408,156, filed Aug. 20,            2021, which is incorporated by reference in its entirety;            and        -   U.S. patent application Ser. No. 17/233,107, filed Apr. 16,            2021, all of which is incorporated by reference in its            entirety;    -   (e) U.S. patent application Ser. No. 17/534,061, filed Nov. 23,        2021, which is incorporated by reference in its entirety;    -   (f) U.S. Patent Application No. 63/344,445, filed May 20, 2022,        which is incorporated by reference in its entirety;    -   (g) U.S. patent application Ser. No. 17/857,920, filed Jul. 5,        2022, which is incorporated by reference in its entirety;    -   (h) U.S. Patent Application No. 63/400,138, filed Aug. 23, 2022,        which is incorporated by reference in its entirety;    -   (i) U.S. patent application Ser. No. 17/940,898, filed Sep. 8,        2022, which is incorporated by reference in its entirety;    -   (j) U.S. patent application Ser. No. 17/941,907, filed Sep. 9,        2022, which is incorporated by reference in its entirety;    -   (k) U.S. patent application Ser. No. 17/957,881, filed Sep. 30,        2022, which is incorporated by reference in its entirety;    -   (l) U.S. patent application Ser. No. 17/990,491, filed Nov. 18,        2022, which is incorporated by reference in its entirety;    -   (m) U.S. patent application Ser. No. 18/130,285, filed Apr. 3,        2023, which is incorporated by reference in its entirety;    -   (n) U.S. patent application Ser. No. 18/134,950, filed Apr. 14,        2023, which is incorporated by reference in its entirety;    -   (o) U.S. patent application Ser. No. 18/196,807, filed May 12,        2023, which is incorporated by reference in its entirety;    -   (p) U.S. patent application Ser. No. 18/196,912, filed May 12,        2023, which is incorporated by reference in its entirety;    -   (q) U.S. patent application Ser. No. 18/196,931, filed May 12,        2023, which is incorporated by reference in its entirety;    -   (r) U.S. patent application Ser. No. 18/196,765, filed May 12,        2023, which is incorporated by reference in its entirety;    -   (s) U.S. patent application Ser. No. 18/196,944, filed May 12,        2023, which is incorporated by reference in its entirety;    -   (t) U.S. patent application Ser. No. 18/196,786, filed May 12,        2023, which is incorporated by reference in its entirety;    -   (u) U.S. patent application Ser. No. 18/196,936, filed May 12,        2023, which is incorporated by reference in its entirety;    -   (v) U.S. patent application Ser. No. 18/198,025, filed May 16,        2023, which is incorporated by reference in its entirety;    -   (w) U.S. patent application Ser. No. 18/198,152, filed May 16,        2023, which is incorporated by reference in its entirety; and    -   (x) U.S. patent application Ser. No. 18/198,671, filed May 17,        2023, which is incorporated by reference in its entirety.

TECHNICAL FIELD

The present invention generally relates to position determination, andmore specifically to determining relative position between vehicles.

BACKGROUND

Mobile Ad-hoc NETworks (MANET; e.g., “mesh networks”) are known in theart as quickly deployable, self-configuring wireless networks with nopre-defined network topology. Each communications node within a MANET ispresumed to be able to move freely. Additionally, each communicationsnode within a MANET may be required to forward (relay) data packettraffic. Data packet routing and delivery within a MANET may depend on anumber of factors including, but not limited to, the number ofcommunications nodes within the network, communications node proximityand mobility, power requirements, network bandwidth, user trafficrequirements, timing requirements, and the like.

MANETs face many challenges due to the limited network awarenessinherent in such highly dynamic, low-infrastructure communicationsystems. Given the broad ranges in variable spaces, the challenges liein making good decisions based on such limited information. For example,in static networks with fixed topologies, protocols can propagateinformation throughout the network to determine the network structure,but in dynamic topologies this information quickly becomes stale andmust be periodically refreshed. It has been suggested that directionalsystems are the future of MANETs, but the potential of this future hasnot as yet been fully realized. In addition to topology factors,fast-moving platforms (e.g., communications nodes moving relative toeach other) experience a frequency Doppler shift (e.g., offset) due tothe relative radial velocity between each set of nodes. This Dopplerfrequency shift often limits receive sensitivity levels which can beachieved by a node within a mobile network.

Therefore, it would be advantageous to provide a device, system, andmethod that cures the shortcomings described above.

SUMMARY

A system is described, in accordance with one or more embodiments of thepresent disclosure. The system includes a transmitter node and areceiver node. Each node of the transmitter node and the receiver nodecomprises a communications interface comprising at least one antennaelement. Each node of the transmitter node and the receiver nodecomprises a controller operatively coupled to the communicationsinterface. The controller includes one or more processors. Thecontroller has information of own node velocity and own nodeorientation. Each node of the transmitter node and the receiver node aretime synchronized to apply Doppler corrections associated with saidnode's own motions relative to a stationary common inertial referenceframe. The stationary common inertial reference frame is known to thetransmitter node and the receiver node prior to the transmitter nodetransmitting a plurality of signals to the receiver node and prior tothe receiver node receiving the plurality of signals from thetransmitter node. The receiver node is configured to digitize theplurality of signals using a step size, determine a modulation amplitudeof the plurality of signals, and adjust the step size based on themodulation amplitude.

This Summary is provided solely as an introduction to subject matterthat is fully described in the Detailed Description and Drawings. TheSummary should not be considered to describe essential features nor beused to determine the scope of the Claims. Moreover, it is to beunderstood that both the foregoing Summary and the following DetailedDescription are example and explanatory only and are not necessarilyrestrictive of the subject matter claimed.

BRIEF DESCRIPTION OF THE DRAWINGS

Implementations of the concepts disclosed herein may be betterunderstood when consideration is given to the following detaileddescription thereof. Such description makes reference to the includeddrawings, which are not necessarily to scale, and in which some featuresmay be exaggerated and some features may be omitted or may berepresented schematically in the interest of clarity. Like referencenumerals in the drawings may represent and refer to the same or similarelement, feature, or function. In the drawings:

FIG. 1 is a diagrammatic illustration of two nodes in a simplifiedmobile ad hoc network (MANET) and individual nodes thereof according toexample embodiments of this disclosure.

FIG. 2A is a graphical representation of frequency shift profiles withinthe MANET of FIG. 1 .

FIG. 2B is a graphical representation of frequency shift profiles withinthe MANET of FIG. 1 .

FIG. 3 is a diagrammatic illustration of a transmitter node and areceiver node according to example embodiments of this disclosure.

FIG. 4A is a graphical representation of frequency shift profiles withinthe MANET of FIG. 3 .

FIG. 4B is a graphical representation of frequency shift profiles withinthe MANET of FIG. 3 .

FIG. 5 is a graph of sets for covering space.

FIG. 6 is a diagrammatic illustration of a transmitter node and areceiver node according to example embodiments of this disclosure.

FIG. 7 is a flow diagram illustrating a method according to exampleembodiments of this disclosure.

FIG. 8 is simplified diagram of a system including receiver nodesembodied in one or more platforms, in accordance with one or moreembodiments of the present disclosure.

FIGS. 9-12 are graphs, in accordance with one or more embodiments of thepresent disclosure.

FIG. 13 is a flow diagram of a method, in accordance with one or moreembodiments of the present disclosure.

DETAILED DESCRIPTION OF THE INVENTION

Before explaining one or more embodiments of the disclosure in detail,it is to be understood that the embodiments are not limited in theirapplication to the details of construction and the arrangement of thecomponents or steps or methodologies set forth in the followingdescription or illustrated in the drawings. In the following detaileddescription of embodiments, numerous specific details are set forth inorder to provide a more thorough understanding of the disclosure.However, it will be apparent to one of ordinary skill in the art havingthe benefit of the instant disclosure that the embodiments disclosedherein may be practiced without some of these specific details. In otherinstances, well-known features may not be described in detail to avoidunnecessarily complicating the instant disclosure.

As used herein a letter following a reference numeral is intended toreference an embodiment of the feature or element that may be similar,but not necessarily identical, to a previously described element orfeature bearing the same reference numeral (e.g., 1, 1 a, 1 b). Suchshorthand notations are used for purposes of convenience only and shouldnot be construed to limit the disclosure in any way unless expresslystated to the contrary.

Further, unless expressly stated to the contrary, “or” refers to aninclusive or and not to an exclusive or. For example, a condition A or Bis satisfied by any one of the following: A is true (or present) and Bis false (or not present), A is false (or not present) and B is true (orpresent), and both A and B are true (or present).

In addition, use of “a” or “an” may be employed to describe elements andcomponents of embodiments disclosed herein. This is done merely forconvenience and “a” and “an” are intended to include “one” or “at leastone,” and the singular also includes the plural unless it is obviousthat it is meant otherwise.

Finally, as used herein any reference to “one embodiment” or “someembodiments” means that a particular element, feature, structure, orcharacteristic described in connection with the embodiment is includedin at least one embodiment disclosed herein. The appearances of thephrase “in some embodiments” in various places in the specification arenot necessarily all referring to the same embodiment, and embodimentsmay include one or more of the features expressly described orinherently present herein, or any combination or sub-combination of twoor more such features, along with any other features which may notnecessarily be expressly described or inherently present in the instantdisclosure.

Reference will now be made in detail to the subject matter disclosed,which is illustrated in the accompanying drawings. Doppler Null Steering(DNS) and Doppler Null Spatial Awareness (DNSA) allows nodes to adjusttransmitted and received frequencies to create a Doppler Null in adesired location. The DNS and/or DNSA protocols can be used to findrelative bearing between transmitter nodes and receiver nodes where oneor both nodes are moving.

Embodiments of the present disclosure are generally directed to adaptivedoppler-nulling digitization for high-resolution. Platforms experiencingsignificantly different Doppler effects can be accommodated by a commonreceiving node. A DNSA transmitter introduces modulation amounts onlyaccording to its own platform Doppler effects. A corresponding receiver,however, may need to accommodate both relatively fast-moving platformsand relatively slow-moving platforms while simultaneously providing fastdiscovery, good sensitivity, and high accuracy for each platform type.

Adjustments are made to various Doppler needs using adaptivedigitization. A high-resolution analog-to-digital process can beemployed for slow-moving platforms, while an analog-to-digital processhaving much larger quantization steps can be used for fast movingplatforms. The adaptive digitization provides the ability to use asingle Doppler-nulling receiving system for a wide range of potentialplatforms—from relatively slow-moving vehicles such as automobiles, tovery fast-moving vehicles such as Low-Earth-Orbit (LEO) satellites.

As described in U.S. patent application Ser. No. 18/130,285, filed Apr.3, 2023, which is herein incorporated by reference in its entirety,embodiments may utilize time synchronized scanning sequences (along withdirectionality) to improve metrics such as signal-to-noise ratio, signalacquisition time, speed of attaining situational awareness of attributesof surrounding nodes, range, and the like. In some embodiments, a zerovalue or near zero value (e.g., or the like such as a zero crossing) ofa calculated net frequency shift of a received signal is used todetermine a bearing angle between the source (e.g., Tx node) and thereceiving node using a time-of-arrival of the received signal. Thebearing angle may be made more accurate by combining (e.g., averaging)it with another bearing angle estimation determined from an angle ofpeak amplitude gain of the signal.

It is noted that U.S. patent application Ser. No. 17/857,920, filed Jul.5, 2022, is at least partially reproduced by at least some (or all) ofthe illustrations of FIGS. 1-7 and at least some (or all) of thecorresponding language for FIGS. 1-7 below. For example, at least someexamples of doppler nulling methods and systems may be betterunderstood, in a nonlimiting manner, by reference to FIGS. 1-7 . Suchembodiments and examples are provided for illustrative purposes and arenot to be construed as necessarily limiting. For instance, inembodiments the transmitter node may be stationary rather than movingand/or vice versa.

Moreover, and stated for purposes of navigating the disclosure only andnot to be construed as limiting, descriptions that may relate to otherlanguage not necessarily reproduced from U.S. patent application Ser.No. 17/857,920 include the discussion and figures after FIGS. 1-7 .

Referring now to FIGS. 1-7 , in some embodiments, a stationary receivermay determine a cooperative transmitter's direction and velocity vectorby using a Doppler null scanning approach in two dimensions. A benefitof the approach is the spatial awareness without exchanging explicitpositional information. Other benefits include discovery,synchronization, and Doppler corrections which are important forcommunications. Some embodiment may combine coordinated transmitterfrequency shifts along with the transmitter's motion induced Dopplerfrequency shift to produce unique net frequency shift signalcharacteristics resolvable using a stationary receiver to achievespatial awareness. Further, some embodiment may include athree-dimensional (3D) approach with the receiver and the transmitter inmotion.

Some embodiments may use analysis performed in a common reference frame(e.g., a common inertial reference frame, such as the Earth, which mayignore the curvature of Earth), and it is assumed that thecommunications system for each of the transmitter and receiver isinformed by the platform of its own velocity and orientation. Theapproach described herein can be used for discovery and tracking, butthe discussion here focuses on discovery which is often the mostchallenging aspect.

The meaning of the Doppler Null′ can be explained in part through areview of the two-dimensional (2D) case without the receiver motion, andthen may be expounded on by a review of adding the receiver motion tothe 2D case, and then including receiver motion in the 3D case.

The Doppler frequency shift of a communications signal is proportionalto the radial velocity between transmitter and receiver, and anysignificant Doppler shift is typically a hindrance that should beconsidered by system designers. In contrast, some embodiments utilizethe Doppler effect to discriminate between directions with theresolution dictated by selected design parameters. Furthermore, suchembodiments use the profile of the net frequency shift as thepredetermined ‘Null’ direction scans through the angle space. Theresultant profile is sinusoidal with an amplitude that provides thetransmitter's speed, a zero net frequency shift when the ‘Null’direction aligns with the receiver, and a minimum indicating thedirection of the transmitter's velocity. It should be noted that thatthe transmitter cannot correct for Doppler in all directions at one timeso signal characteristics are different in each direction and aredifferent for different transmitter velocities as well. It is exactlythese characteristics that the receiver uses to determine spatialawareness. The received signal has temporal spatial characteristics thatcan be mapped to the transmitter's direction and velocity. This approachutilizes the concept of a ‘Null’ which is simply the direction where thetransmitter perfectly corrects for its own Doppler shift. The same‘Nulling’ protocol runs on each node and scans through all directions,such as via a scanning sequence of a protocol. Here we arbitrarilyillustrate the scanning with discrete successive steps of 10 degrees butin a real system; however, it should be understood that any suitablestep size of degrees may be used for Doppler null scanning.

As already mentioned, one of the contributions of some embodiments ispassive spatial awareness. Traditionally, spatial information forneighbor nodes (based on a global positioning system (GPS) and/or gyrosand accelerometers) can be learned via data communication.Unfortunately, spatial awareness via data communication, referred to asactive spatial awareness is possible only after communication hasalready been established, not while discovering those neighbor nodes.Data communication is only possible after the signals for neighbor nodeshave been discovered, synchronized and Doppler corrected. In contrast,in some embodiments, the passive spatial awareness described herein maybe performed using only synchronization bits associated withacquisition. This process can be viewed as physical layer overhead andtypically requires much lower bandwidth compared to explicit datatransfers. The physical layer overheads for discovery, synchronizationand Doppler correction have never been utilized for topology learningfor upper layers previously.

Traditionally, network topology is harvested via a series of data packetexchanges (e.g., hello messaging and link status advertisements). Thepassive spatial awareness may eliminate hello messaging completely andprovide a wider local topology which is beyond the coverage of hellomessaging. By utilizing passive spatial awareness, highly efficientmobile ad hoc networking (MANET) is possible. Embodiments may improvethe functioning of a network, itself.

Referring to FIG. 1 , a multi-node communications network 100 isdisclosed. The multi-node communications network 100 may includemultiple communications nodes, e.g., a transmitter (Tx) node 102 and areceiver (Rx) node 104.

In embodiments, the multi-node communications network 100 may includeany multi-node communications network known in the art. For example, themulti-node communications network 100 may include a mobile ad-hocnetwork (MANET) in which the Tx and Rx nodes 102, 104 (as well as everyother communications node within the multi-node communications network)is able to move freely and independently. Similarly, the Tx and Rx nodes102, 104 may include any communications node known in the art which maybe communicatively coupled. In this regard, the Tx and Rx nodes 102, 104may include any communications node known in the art fortransmitting/transceiving data packets. For example, the Tx and Rx nodes102, 104 may include, but are not limited to, radios (such as on avehicle or on a person), mobile phones, smart phones, tablets, smartwatches, laptops, and the like. In embodiments, the Rx node 104 of themulti-node communications network 100 may each include, but are notlimited to, a respective controller 106 (e.g., control processor),memory 108, communication interface 110, and antenna elements 112. (Inembodiments, all attributes, capabilities, etc. of the Rx node 104described below may similarly apply to the Tx node 102, and to any othercommunication node of the multi-node communication network 100.)

In embodiments, the controller 106 provides processing functionality forat least the Rx node 104 and can include any number of processors,micro-controllers, circuitry, field programmable gate array (FPGA) orother processing systems, and resident or external memory for storingdata, executable code, and other information accessed or generated bythe Rx node 104. The controller 106 can execute one or more softwareprograms embodied in a non-transitory computer readable medium (e.g.,memory 108) that implement techniques described herein. The controller106 is not limited by the materials from which it is formed or theprocessing mechanisms employed therein and, as such, can be implementedvia semiconductor(s) and/or transistors (e.g., using electronicintegrated circuit (IC) components), and so forth.

In embodiments, the memory 108 can be an example of tangible,computer-readable storage medium that provides storage functionality tostore various data and/or program code associated with operation of theRx node 104 and/or controller 106, such as software programs and/or codesegments, or other data to instruct the controller 106, and possiblyother components of the Rx node 104, to perform the functionalitydescribed herein. Thus, the memory 108 can store data, such as a programof instructions for operating the Rx node 104, including its components(e.g., controller 106, communication interface 110, antenna elements112, etc.), and so forth. It should be noted that while a single memory108 is described, a wide variety of types and combinations of memory(e.g., tangible, non-transitory memory) can be employed. The memory 108can be integral with the controller 106, can comprise stand-alonememory, or can be a combination of both. Some examples of the memory 108can include removable and non-removable memory components, such asrandom-access memory (RAM), read-only memory (ROM), flash memory (e.g.,a secure digital (SD) memory card, a mini-SD memory card, and/or amicro-SD memory card), solid-state drive (SSD) memory, magnetic memory,optical memory, universal serial bus (USB) memory devices, hard diskmemory, external memory, and so forth.

In embodiments, the communication interface 110 can be operativelyconfigured to communicate with components of the Rx node 104. Forexample, the communication interface 110 can be configured to retrievedata from the controller 106 or other devices (e.g., the Tx node 102and/or other nodes), transmit data for storage in the memory 108,retrieve data from storage in the memory, and so forth. Thecommunication interface 110 can also be communicatively coupled with thecontroller 106 to facilitate data transfer between components of the Rxnode 104 and the controller 106. It should be noted that while thecommunication interface 110 is described as a component of the Rx node104, one or more components of the communication interface 110 can beimplemented as external components communicatively coupled to the Rxnode 104 via a wired and/or wireless connection. The Rx node 104 canalso include and/or connect to one or more input/output (I/O) devices.In embodiments, the communication interface 110 includes or is coupledto a transmitter, receiver, transceiver, physical connection interface,or any combination thereof.

It is contemplated herein that the communication interface 110 of the Rxnode 104 may be configured to communicatively couple to additionalcommunication interfaces 110 of additional communications nodes (e.g.,the Tx node 102) of the multi-node communications network 100 using anywireless communication techniques known in the art including, but notlimited to, GSM, GPRS, CDMA, EV-DO, EDGE, WiMAX, 3G, 4G, 4G LTE, 5G,Wi-Fi protocols, RF, LoRa, and the like.

In embodiments, the antenna elements 112 may include directional oromnidirectional antenna elements capable of being steered or otherwisedirected (e.g., via the communications interface 110) for spatialscanning in a full 360-degree arc (114) relative to the Rx node 104 (oreven less than a full 360-degree arc).

In embodiments, the Tx node 102 and Rx node 104 may one or both bemoving in an arbitrary direction at an arbitrary speed, and maysimilarly be moving relative to each other. For example, the Tx node 102may be moving relative to the Rx node 104 according to a velocity vector116 (|{right arrow over (V_(T))}|), at a relative velocity VT and arelative angular direction (an angle α relative to an arbitrarydirection 118 (e.g., due east); θ may be the angular direction of the Rxnode relative to due east.

In embodiments, the Tx node 102 may implement a Doppler nullingprotocol. For example, the Tx node 102 may adjust its transmit frequencyto counter the Doppler frequency offset such that there is no netfrequency offset (e.g., “Doppler null”) in a Doppler nulling direction120 (e.g., at an angle ϕ relative to the arbitrary direction 118). Thetransmitting waveform (e.g., the communications interface 110 of the Txnode 102) may be informed by the platform (e.g., the controller 106) ofits velocity vector and orientation (e.g., α, |{right arrow over(V_(T))}|) and may adjust its transmitting frequency to remove theDoppler frequency shift at each Doppler nulling direction 120 and angleϕ.

To illustrate aspects of some embodiments, we show the 2D dependence ofthe net frequency shift for a stationary receiver as a function of Nulldirection across the horizon, as shown in a top-down view of FIG. 1 ,where the receiver node 104 is stationary and positioned θ from eastrelative to the transmitter, the transmitter node 102 is moving with aspeed |{right arrow over (V_(T))}| and direction α from east and asnapshot of the scanning φ which is the ‘Null’ direction, exemplarilyshown as 100 degrees in this picture.

The Doppler shift is a physical phenomenon due to motion and can beconsidered as a channel effect. In this example the transmitter node 102is the only moving object, so it is the only source of Doppler shift.The Doppler frequency shift as seen by the receiver node 104 due to thetransmitter node 102 motion is:

${\frac{\Delta f_{DOPPLER}}{f} = {\frac{❘\overset{\longrightarrow}{V_{T}}❘}{c}\cos( {\theta - \alpha} )}},$

where c is the speed of light.

The other factor is the transmitter frequency adjustment term thatshould exactly compensate the Doppler shift when the ‘Null’ directionaligns with the receiver direction. It is the job of the transmitternode 102 to adjust its transmit frequency according to its own speed(|{right arrow over (V_(T))}|), and velocity direction α. Thattransmitter frequency adjustment (Δf_(T)) is proportional to thevelocity projection onto the ‘Null’ direction φ (120) and is:

$\frac{\Delta f_{T}}{f} = {{- \frac{❘\overset{\longrightarrow}{V_{T}}❘}{c}}\cos{( {\varphi - \alpha} ).}}$

The net frequency shift seen by the receiver is the sum of the twoterms:

$\frac{\Delta f_{net}}{f} = {{\frac{❘\overset{\longrightarrow}{V_{T}}❘}{c}\lbrack {{\cos( {\theta - \alpha} )} - {\cos( {\varphi - \alpha} )}} \rbrack}.}$

It is assumed that the velocity vector and the direction changes slowlycompared to the periodic measurement of Δf_(net). Under thoseconditions, the unknown parameters (from the perspective of the receivernode 104) of α, |{right arrow over (V_(T))}|, and θ are constants.

Furthermore, it is assumed that the receiver node 104 has animplementation that resolves the frequency of the incoming signal, aswould be understood to one of ordinary skill in the art.

FIG. 2A shows the resulting net frequency shift as a function of the‘Null’ direction φ (120) for scenarios where a stationary receiver isdue east of the transmitter (θ=0), and assuming a transmitter speed|{right arrow over (V_(T))}| of 1500 meters per second (m/s). FIG. 2Bshows the results for a stationary receiver and for several directionswith a due-east transmitter node velocity direction (α=0). The frequencyshifts are in units of parts per million (ppm). As shown in FIGS. 2A and2B, the amplitude is consistent with the transmitter node's 102 speed of5 ppm [|{right arrow over (V_(T))}|/c*(1×106)] regardless of thevelocity direction or position, the net frequency shift is zero when the‘Null’ angle is in the receiver direction (when φ=8), and the minimumoccurs when the ‘Null’ is aligned with the transmitter node's 102velocity direction (when φ=α).

From the profile, the receiver node 104 can therefore determine thetransmitter node's 102 speed, the transmitter node's 102 heading, andthe direction of the transmitter node 102 is known to at most, one oftwo locations (since some profiles have two zero crossings). It shouldbe noted that the two curves cross the y axis twice (0 & 180 degrees inFIG. 2A, and ±90 degrees in FIG. 2B) so there is initially an instanceof ambiguity in position direction. In this case the receiver node 104knows the transmitter node 102 is either East or West of the receivernode 104.

Referring to FIG. 3 , a multi-node communications network 100 isdisclosed. The multi-node communications network 100 may includemultiple communications nodes, e.g., a transmitter (Tx) node 102 and areceiver (Rx) node 104. As shown in FIG. 3 both of the transmitter node102 and the receiver node 104 are in motion in two dimensions.

The simultaneous movement scenario is depicted in FIG. 3 where thereceiver node 104 is also moving in a generic velocity characterized bya speed |{right arrow over (V_(R))}| and the direction β relative to dueeast. The protocol for the moving receiver node 104 incorporates afrequency adjustment on the receiver node's 104 side to compensate forthe receiver node's motion as well. The equations have two additionalterms. One is a Doppler term for the motion of the receiver, and thesecond is frequency compensation by the receiver.

Again, the Doppler shift is a physical phenomenon due to motion and canbe considered as a channel effect, but in this case both the transmitternode 102 and the receiver node 104 are moving, so there are two Dopplershift terms. The true Doppler shift as seen by the receiver due to therelative radial velocity is:

$\frac{\Delta f_{DOPPLER}}{f} = {{\frac{❘\overset{\longrightarrow}{V_{T}}❘}{c}\cos( {\theta - \alpha} )} - {\frac{❘\overset{\longrightarrow}{V_{R}}❘}{c}\cos{( {\theta - \beta} ).}}}$

The other factors are the transmitter node 102 and receiver node 104frequency adjustment terms that exactly compensate the Doppler shiftwhen the ‘Null’ direction aligns with the receiver direction (e.g., whenφ=β). It is the job of the transmitter node 102 to adjust thetransmitter node's 102 transmit frequency according to its own speed(|{right arrow over (V_(T))}|), and velocity direction α. Thattransmitter node frequency adjustment is proportional to the velocityprojection onto the ‘Null’ direction φ and is the first term in theequation below.

It is the job of the receiver node 104 to adjust the receiver nodefrequency according to the receiver node's 104 own speed (|{right arrowover (V_(R))}|), and velocity direction β. That receiver node frequencyadjustment is proportional to the velocity projection onto the ‘Null’direction φ and is the second term in the equation below. The receivernode frequency adjustment can be done to the receive signal prior to thefrequency resolving algorithm or could be done within the algorithm.

$\frac{\Delta f_{{T\&}R}}{f} = {{{- \frac{❘\overset{\longrightarrow}{V_{T}}❘}{c}}\cos( {\varphi - \alpha} )} + {\frac{❘\overset{\longrightarrow}{V_{R}}❘}{c}\cos{( {\varphi - \beta} ).}}}$

The net frequency shift seen by the receiver is the sum of all terms:

$\frac{\Delta f_{net}}{f} = {{\frac{❘\overset{\longrightarrow}{V_{T}}❘}{c}\lbrack {{\cos( {\theta - \alpha} )} - {\cos( {\varphi - \alpha} )}} \rbrack} - {{\frac{❘\overset{\longrightarrow}{V_{R}}❘}{c}\lbrack {{\cos( {\theta - \beta} )} - {\cos( {\varphi - \beta} )}} \rbrack}.}}$

Again, it is assumed that the receiver node 104 has an implementationthat resolves the frequency of the incoming signal, as would beunderstood in the art.

Also, it is assumed that the velocity vector and direction changesslowly compared to the periodic measurement of Δf_(net). Again, undersuch conditions, the unknown parameters (from the perspective of thereceiver node 104) α, |{right arrow over (V_(T))}|, and θ are constants.When the velocity vector or direction changes faster, this change couldbe tracked, for example if the change is due to slow changes inacceleration.

Referring now to FIGS. 4A-4B.

The net frequency shift for the two-dimensional (2D) moving receivernode 104 approach is shown in FIGS. 4A and 4B for several scenario casesof receiver node location 8, transmitter node and receiver node speeds(|{right arrow over (V_(T))}| & |{right arrow over (V_(R))}|), andtransmitter node and receiver node velocity directions α and βrespectively. FIG. 4A shows different speeds for the transmitter node102 and receiver node 104 as well as the receiver node location of θ=0.FIG. 4B assumes the same speed (e.g., 1500 m/s) for the transmitter nodeand receiver node. Similarly, there are three concepts to notice here:

First, the amplitude is consistent with the relative velocity betweentransmitter node 102 and receiver node 104.

$\frac{❘( {{{❘\overset{\longrightarrow}{V_{T}}❘}\cos\alpha} - {{❘\overset{\longrightarrow}{V_{R}}❘}\cos\beta}} )❘}{c*1e^{6}}.$

Second, the net frequency shift is zero when the ‘Null’ angle is in thereceiver direction, e.g., when φ=8.

Third, the minimum occurs when the ‘Null’ angle is aligned with therelative velocity direction, e.g., when φ=angle (|{right arrow over(V_(T))}| cos α−|{right arrow over (V_(R))}| cos β).

Again, there is an initial dual point ambiguity with the position θ, butthe transmitter node's 102 speed and velocity vector are known.

Referring now to FIG. 5 , while the 2D picture is easier to visualize,the same principles apply to the 3D case. FIG. 5 shows a number ofdirection sets needed to span 3D and 2D space with different cone sizes(cone sizes are full width). Before diving into the equations, it'sworth commenting on the size of the space when including anotherdimension. For example, when a ‘Null’ step size of 10 degrees was usedin the previous examples, it took 36 sets to span the 360 degrees in 2D.Thus, if an exemplary detection angle of 10 degrees is used (e.g., adirectional antenna with 10-degree cone) it would take 36 sets to coverthe 2D space. The 3D fractional coverage can be computed by calculatingthe coverage of a cone compared to the full 4π pi steradians. Thefraction is equal to the integral

${{Fraction}{Coverage}3D} = {{\int_{0}^{\frac{{Cone}{Size}}{2}}\frac{r^{2}\sin({\theta\prime})d{\theta\prime}d\varphi}{4\pi r^{2}}} = \frac{1 - {\cos( \frac{{Cone}{Size}}{2} )}}{2}}$${{Fraction}{Coverage}2D} = \frac{2\pi}{{Cone}{Size}}$

The number of sets to span the space is shown in FIG. 5 for both the 2Dand 3D cases, which correlates with discovery time. Except for narrowcone sizes, the number of sets is not drastically greater for the 3Dcase (e.g., approximately 15 times at 10 degrees, 7 time at 20 degrees,and around 5 times at 30 degrees). Unless systems are limited to verynarrow cone sizes, the discovery time for 3D searches is notoverwhelming compared to a 2D search.

Referring now to FIG. 6 , a multi-node communications network 100 isdisclosed. The multi-node communications network 100 may includemultiple communications nodes, e.g., a transmitter (Tx) node 102 and areceiver (Rx) node 104. As shown in FIG. 6 both the transmitter node 102and the receiver node 104 are in motion in three dimensions.

The 3D approach to Doppler nulling follows the 2D approach but it isillustrated here with angles and computed vectorially for simplicity.

In three dimensions, it is convenient to express the equations in vectorform which is valid for 2 or 3 dimensions. FIG. 6 shows the geometry in3 dimensions where

is the unit vector pointing to the receiver from the transmitter, and

is the unit vector pointing in the ‘Null’ direction defined by theprotocol.

The true Doppler shift as seen by the receiver node 104 due to therelative radial velocity which is the projection onto the

vector:

$\frac{\Delta f_{DOPPLER}}{f} = {{\frac{1}{c}{\overset{arrow}{V_{T}} \cdot}} - {\frac{1}{c}{\overset{arrow}{V_{R}} \cdot .}}}$

The nulling protocol adjusts the transmit node frequency and receivernode frequency due to their velocity projections onto the

direction

$\frac{\Delta f_{T}}{f} = {{{- \frac{1}{c}}{\overset{arrow}{V_{T}} \cdot}} + {\frac{1}{c}{\overset{arrow}{V_{R}} \cdot .}}}$

The net frequency shift seen by the receiver node 104 is the sum of allterms:

$\frac{\Delta f_{net}}{f} = {{\frac{1}{c}{\overset{arrow}{V_{T}} \cdot}} - {\frac{1}{c}{\overset{arrow}{V_{R}} \cdot}} - {\frac{1}{c}{\overset{arrow}{V_{T}} \cdot}} + {\frac{1}{c}{\overset{arrow}{V_{R}} \cdot .}}}$

The net frequency shift for the 3D moving receiver node 104 approach isnot easy to show pictorially but can be inspected with mathematicalequations to arrive at useful conclusions. The first two terms are theDoppler correction (DC) offset and the last two terms are the nulldependent terms. Since the

is the independent variable, the maximum occurs when ({right arrow over(V_(R))}−{right arrow over (V_(T))}) and

are parallel and is a minimum when they are antiparallel. Furthermore,the relative speed is determined by the amplitude

${Amplitude} = {\frac{❘{\overset{\longrightarrow}{V_{R}} - \overset{\longrightarrow}{V_{T}}}❘}{c}.}$

Lastly, the net frequency is zero when the

is parallel (i.e., parallel in same direction, as opposed toanti-parallel) to

:

${\frac{\Delta f_{net}}{f} = {{{0{when}\frac{1}{c}{\overset{arrow}{V_{T}} \cdot}} - {\frac{1}{c}{\overset{arrow}{V_{R}} \cdot}}} = {{\frac{1}{c}{\overset{arrow}{V_{T}} \cdot}} - {\frac{1}{c}{\overset{arrow}{V_{R}} \cdot}{or}}}}},$

For the 3D case:

The amplitude is consistent with the relative velocity betweentransmitter node 102 and receiver node 104

$\lbrack \frac{❘{\overset{\longrightarrow}{V_{R}} - \overset{\longrightarrow}{V_{T}}}❘}{c} \rbrack.$

The net frequency shift is zero when the ‘Null’ angle is in the receivernode direction, e.g., ({right arrow over (V_(T))}−{right arrow over(V_(R))})·

=({right arrow over (V_(T))}−{right arrow over (V_(R))})·

).

The minimum occurs when the ‘Null’ is aligned with the relative velocitydirection.

Referring still to FIG. 6 , in some embodiments, the system (e.g., themulti-node communications network 100) may include a transmitter node102 and a receiver node 104. Each node of the transmitter node 102 andthe receiver node 104 may include a communications interface 110including at least one antenna element 112 and a controller operativelycoupled to the communications interface, the controller 106 includingone or more processors, wherein the controller 106 has information ofown node velocity and own node orientation. The transmitter node 102 andthe receiver node 104 may be in motion (e.g., in two dimensions or inthree dimensions). The transmitter node 102 and the receiver node 104may be time synchronized to apply Doppler corrections associated withsaid node's own motions relative to a common reference frame (e.g., acommon inertial reference frame (e.g., a common inertial reference framein motion or a stationary common inertial reference frame)). The commonreference frame may be known to the transmitter node 102 and thereceiver node 104 prior to the transmitter node 102 transmitting signalsto the receiver node 104 and prior to the receiver node 104 receivingthe signals from the transmitter node 102. In some embodiments, thesystem is a mobile ad-hoc network (MANET) comprising the transmitternode 102 and the receiver node 104.

In some embodiments, the applying of the Doppler corrections associatedwith the receiver node's own motions relative to the common referenceframe is based on a common reference frequency. For example, a commonreference frequency may be adjusted by a node's own motions to cancelout those motions in reference to the null angle. This common referencefrequency may be known by each node prior to transmission and/orreception of the signals. In some embodiments, calculating the netfrequency change seen by the receiver node 104 is based on the commonreference frequency. For example, the net frequency change may be adifference between a measured frequency of the signals and the commonreference frequency.

For purposes of discussing the receiver node 104, a “source” generallyrefers to a source of a received signal, multiple sources of multiplesignals, a single source of multiple signals, and/or the like. Forexample, a source may be a transmitter node 102 configured to applyDoppler corrections as disclosed herein and in applications from whichpriority is claimed and/or incorporated by reference. In this regard, areceiver node 104 may determine one or more attributes of the source(e.g., bearing between the receiver node 104 and the source, bearing ofthe velocity of the source, amplitude/speed of the velocity, range, andthe like). In some embodiments, the receiver node 104 and the source(e.g., transmitter node 102) are configured to use a same, compatible,and/or similar Doppler correction, protocol, common reference frame,common reference frequency, time synchronization, and/or the like suchthat the receiver node 104 may determine various attributes of thesource. Note, in some embodiments, that one or more of these may beknown ahead of time, be determined thereafter, included as fixedvariable values as part of the protocol, and/or determined dynamically(in real time) as part of the protocol. For example, the protocol maydetermine that certain common reference frames should be used in certainenvironments, such as using GPS coordinates on land and a naval shipbeacon transmitter common reference frame location (which may be mobile)over certain areas of ocean, which may dynamically change in real timeas a location of a node changes.

In some embodiments, the transmitter node 102 and the receiver node 104are time synchronized via synchronization bits associated withacquisition. For example, the synchronization bits may operate asphysical layer overhead.

In some embodiments, the transmitter node 102 is configured to adjust atransmit frequency according to an own speed and an own velocitydirection of the transmitter node 102 so as to perform atransmitter-side Doppler correction. In some embodiments, the receivernode 104 is configured to adjust a receiver frequency of the receivernode 104 according to an own speed and an own velocity direction of thereceiver node 104 so as to perform a receiver-side Doppler correction.In some embodiments, an amount of adjustment of the adjusted transmitfrequency is proportional to a transmitter node 102 velocity projectiononto a Doppler null direction, wherein an amount of adjustment of theadjusted receiver frequency is proportional to a receiver node 104velocity projection onto the Doppler null direction. In someembodiments, the receiver node 104 is configured to determine a relativespeed between the transmitter node 102 and the receiver node 104. Insome embodiments, the receiver node 104 is configured to determine adirection that the transmitter node 102 is in motion and a velocityvector of the transmitter node 102. In some embodiments, a maximum netfrequency shift for a Doppler correction by the receiver node 104 occurswhen a resultant vector is parallel to the Doppler null direction,wherein the resultant vector is equal to a velocity vector of thereceiver node 104 minus the velocity vector of the transmitter node 102.In some embodiments, a minimum net frequency shift for a Dopplercorrection by the receiver node 104 occurs when a resultant vector isantiparallel to the Doppler null direction, wherein the resultant vectoris equal to a velocity vector of the receiver node 104 minus thevelocity vector of the transmitter node 102. In some embodiments, a netfrequency shift for a Doppler correction by the receiver node 104 iszero when a vector pointing to the receiver node from the transmitternode 102 is parallel to the Doppler null direction.

Referring now to FIG. 7 , an exemplary embodiment of a method 700according to the inventive concepts disclosed herein may include one ormore of the following steps. Additionally, for example, some embodimentsmay include performing one or more instances of the method 700iteratively, concurrently, and/or sequentially. Additionally, forexample, at least some of the steps of the method 700 may be performedin parallel and/or concurrently. Additionally, in some embodiments, atleast some of the steps of the method 700 may be performednon-sequentially.

A step 702 may include providing a transmitter node and a receiver node,wherein each node of the transmitter node and the receiver node are timesynchronized, wherein each node of the transmitter node and the receivernode are in motion, wherein each node of the transmitter node and thereceiver node comprises a communications interface including at leastone antenna element, wherein each node of the transmitter node and thereceiver node further comprises a controller operatively coupled to thecommunications interface, the controller including one or moreprocessors, wherein the controller has information of own node velocityand own node orientation.

A step 704 may include based at least on the time synchronization,applying, by the transmitter node, Doppler corrections to thetransmitter node's own motions relative to a common reference frame.

A step 706 may include based at least on the time synchronization,applying, by the receiver node, Doppler corrections to the receivernode's own motions relative to the common reference frame, wherein thecommon reference frame is known to the transmitter node and the receivernode prior to the transmitter node transmitting signals to the receivernode and prior to the receiver node receiving the signals from thetransmitter node.

Further, the method 700 may include any of the operations disclosedthroughout.

The null scanning technique discussed herein illustrates a system and amethod for spatial awareness from resolving the temporal spatialcharacteristics of the transmitter node's 102 radiation. This approachinforms the receiver node 104 of the relative speed between thetransmitter node 102 and receiver node 104 as well as the transmitternode direction and transmitter node velocity vector. This approachincludes scanning through all directions and has a high sensitivity(e.g., low net frequency shift) when the null direction is aligned withthe transmitter node direction. This approach can be implemented on ahighly sensitive acquisition frame which is typically much moresensitive than explicit data transfers which allow for theultra-sensitive spatial awareness with relatively low power.

This sentence may mark an end to the (at least partially) reproducedlanguage from U.S. patent application Ser. No. 17/857,920 correspondingto the (at least partially) reproduced FIGS. 1-7 . However, note thatthis paragraph is nonlimiting, and changes may have been made andlanguage added or removed, and not all the language above orcorresponding figures above are necessarily reproduced from U.S. patentapplication Ser. No. 17/857,920.

Examples of doppler nulling methods include, but are not limited to,methods and other descriptions (e.g., at least some theory andmathematical basis) are disclosed in U.S. patent application Ser. No.17/233,107, filed Apr. 16, 2021, which is hereby incorporated byreference in its entirety; U.S. patent application Ser. No. 17/534,061,filed Nov. 23, 2021, which is hereby incorporated by reference in itsentirety; and U.S. patent application Ser. No. 17/857,920, filed Jul. 5,2022, which is hereby incorporated by reference in its entirety. Inembodiments, doppler nulling methods allow for benefits such as, but notlimited to, relatively quickly and/or efficiently detecting transmitternodes and determining transmitter node attributes (e.g., transmitternode speed, transmitter node bearing, relative bearing of transmitternode relative to receiver node, relative distance of transmitter noderelative to receiver node, and the like).

Referring now to FIG. 8 , a system 800 is described, in accordance withone or more embodiments of the present disclosure. The embodiments andenabling technology of the multi-node communications network 100 isincorporated herein by reference as to the system 800. The system 800may include, one or more of the transmitter nodes 102 and receiver nodes104. In some embodiments, the receiver nodes 104 may be embodied withinone or more platforms. For example, the receiver nodes 104 may include aplatform. The platform may be satellite 802, such as, but not limitedto, a low-earth orbit (LEO) satellite. By way of another example, thetransmitter nodes 102 may include an aircraft 804 or another terrestrialplatform.

Each of the satellite 802 and the aircraft 804 may transmit and receivesignals for doppler nulling purposes. The satellite 802 is a relativelya fast-moving platform, such that the signals received by the receivernode 104 experience significant doppler effects. The aircraft 804 is arelatively a slow-moving platform, such that the signals received by thereceiver node 104 experience reduced doppler effects compared to thesatellite 802.

A Doppler-nulling transmitter induces modulation having an amplitudeaccording to its own-platform Doppler effects and may implement themodulation in analog fashion with essentially infinite resolution. Thetransmission of Doppler-nulling modulation may be produced inessentially analog fashion with each transmission's exact frequencyvarying along a continuous spectrum.

The receiver node 104 may receive the signals from the transmitter node.In embodiments, the receiver node 104 may quantize the signals toproduce digital signals. The receiver node 104 may include a quantizerto perform the quantization. For example, the receiver node 104 mayinclude an analog-to-digital converter (ADC) or the like to quantize thesignals. The digitized signals may include a magnitude based on theown-platform Doppler effects. The receiver node 104 is configured todigitize the plurality of signals using a step size. The receiver node104, in order to process the signal with modern signal processingtechniques, digitizes the received signals with finite resolution. Thereceiver node 104 (due to hardware size and power constraints) may belimited to digitization using a finite number of discrete frequencysteps. The receiver node 104 then determines a modulation amplitude ofthe plurality of signals. The modulation amplitude is determined basedon the digitization.

The issue with digitization is that the receiver node 104 needs toaccommodate both very fast-moving platforms exhibiting large Dopplerfrequency shifts and very slow-moving platforms exhibiting only smallDoppler frequency shifts, while simultaneously providing fast discovery,good sensitivity and high accuracy for each platform type. Inembodiments, platforms experiencing significantly different Dopplereffects can be accommodated by the receiver node 104 using one or moremethods of adaptive digitization, as will be described further herein.The receiver node 104 accommodates both relatively fast-moving platformsand relatively slow-moving platforms while simultaneously providing fastdiscovery, good sensitivity, and high accuracy for each platform typeusing the method of adaptive digitization.

Embodiments of the present disclosure describe adjusting to variousDoppler needs using adaptive digitization. The receiver node 104 adjuststhe step size based on the modulation amplitude. The receiver node 104employs adaptive tracking with variable quantization size according tothe modulation amplitude. A high-resolution analog-to-digital processcan be employed for slow-moving platforms, while an analog-to-digitalprocess having much larger quantization steps can be used forfast-moving platforms. The primary benefit provided from this approachis the ability to use a single Doppler-nulling receiving system for awide range of potential platforms—from relatively slow-moving vehiclessuch as automobiles, to very fast-moving vehicles such asLow-Earth-Orbit (LEO) satellites.

The process of detection for Doppler-nulling can involve a highlysensitive frequency selective process which only provides peaksensitivity over the narrow range of frequencies for whichDoppler-nulling can reduce the offset frequency to near zero. Followingthe initial detection, the receiver node 104 tracks the Doppler-nullingmodulation as the frequency increases and decreases in sinusoidalfashion. As Doppler-nulling changes the modulating frequency, thetracking process simultaneously follows the modulating frequency inorder to maintain sensitivity. The process is iteratively performed toachieve the sensitivity.

For, example, when tracking slow-moving platforms (say, for example,having 10 Hz Doppler frequency shift), a small quantization step sizecan be selected, whereas a larger quantization step size can be selectedwhen tracking a fast-moving LEO satellite (say, for example with 10 kHzDoppler frequency shift). In this regard, the doppler shift of thesignals received by the receiver node 104 due to the node's own motionsis between 10 Hz and 10 kHz. It is further contemplated that the dopplershift of the plurality of signals may be between 1 Hz and 10 MHz. Thissimple example illustrates three orders of magnitude difference inquantization size although in each case the same tracking algorithm canprovide the same angular resolution regardless of the associatedplatform Doppler quantization step sizes employed. To a large extent,angular accuracy depends upon the number of quantization steps requiredto cover a vehicle's Doppler effects range, not the specific Dopplerfrequency observed. With a relatively small number of fixed discretefrequency steps, the receiver node 104 may simultaneously provide theresolution needed for both slow-moving platforms, which exhibit smallamounts of Doppler frequency shift and fast-moving platforms whichexhibit large amounts of Doppler frequency shift.

Referring now to FIG. 9 , a graph 900 is described, in accordance withone or more embodiments of the present disclosure. The graph 900provides a quantization example for Doppler-nulling. The Doppler-nullingsignal is depicted as a sinusoidal signal. Tracking of theDoppler-nulling signal, as seen in the quantized reconstruction of theinput sinusoid, begins at about 0.35 seconds. An accurate reconstructionof the signal can be accomplished using only the nine steps seen in thefigure. The sinusoidal nature of Doppler-nulling modulation causes themodulation to be predictable. In particular, the platform may notexperience sufficiently rapid changes in velocity to impact the Dopplerfrequency shift. The future frequencies may then be largely predictablefrom past frequencies. When the observed Doppler-nulling modulationfrequency changes sufficiently, the next digital frequency step isemployed until the frequency again changes sufficiently to take yetanother digital step.

Referring now to FIG. 10 , a graph 1000 is described, in accordance withone or more embodiments of the present disclosure. The graph 1000depicts the transmitted Doppler nulling modulation profile 1002, thereceived digitization 1004 or quantization of the profile 1002 in thereceiver node 104, and a digitized signal 1006. The digitized signal1006 is generated from the received digitization 1004 after resamplingand filtering. The digitized signal 1006 is a high-resolutionreconstruction of the profile 1002. In this regard, the reconstructedsignal closely resembles the original.

Referring now to FIG. 11 , a graph 1100 is described, in accordance withone or more embodiments of the present disclosure. The graph 1100depicts the transmitted Doppler nulling modulation profile 1102, thereceived digitization 1104 or quantization of the profile 1102 in thereceiver node 104, and a digitized signal 1106. The digitized signal1106 is generated from the received digitization 1104 after resamplingand filtering. The received digitization 1104 does not include asufficient step size, such that the digitized signal 1106 does notclosely resemble the profile 1102. This graph 1100 provides an instancewhere maintaining the same digital resolution in the receiver, forplatforms exhibiting different amounts of Doppler, fails to provide anaccurate reproduction of the original profile. The transmitted signalexhibits much lower Doppler shift such that only one quantization stepis available for digitization and the reconstructed digital signal 1106does not accurately represent the original Doppler-nulling signal.

Referring now to FIG. 12 , a graph 1200 is depicted, in accordance withone or more embodiments of the present disclosure. The graph 1200depicts the transmitted Doppler nulling modulation profile 1202, thereceived digitization 1204 or quantization of the profile 1202 in thereceiver node 104, and a digitized signal 1206. The digitized signal1206 is generated from the received digitization 1204 after resamplingand filtering. The received digitization 1204 includes a sufficient stepsize, such that the digitized signal 1206 closely resembles the profile1202.

The receiver node 104 may discern when only a small number ofquantization steps are being employed. The receiver node 104 can, inthis instance, automatically adapt the quantization size to use smallerfrequency steps, as appropriate for the signal being digitized. Adaptingthe quantization size provides a good reproduction of the originalsignal without changing any system parameters other than quantizationstep size. The digitized signal 1206 may then accurately represents theoriginal signal in both amplitude and phase, even though theDoppler-nulling modulation exhibited on the input signal is much smallerthan were seen in earlier figures.

Referring now to FIG. 13 , a flow diagram of a method 1300 is described,in accordance with one or more embodiments of the present disclosure.

In a step 1310, the receiver node 104 recognizes a transmittedDoppler-nulling signal. The receiver node 104 may recognize thetransmitted Doppler-nulling signal as a result of being able tocorrelate on a near zero Doppler signal at the bearing angle of theDoppler-nulling transmitter, or via a similar method.

In a step 1320, the receiver node 104 digitizes the Doppler-nullingsignal. The receiver node 104 digitizes the Doppler-nulling signal usinga step size. The step size may be referred to as a Doppler step size, afrequency step size, a quantization step size, and the like. The stepsize may be initially set at a relatively large step size in order toascertain Doppler-nulling modulation amplitude. A modulation amplitudeis determined from the digitized signal. The observed modulationamplitude is based on both the transmitted node's Doppler-nullingmodulation and the received node's own motions of the receiver node 104.In particular, the modulation amplitude may be proportional to themotion of the transmitter and the receiver node 104. The step size maybe set to a larger amount of time per step to enable determining highermodulation amplitudes, and similarly velocities of nodes with highervelocities (e.g., the satellite 802).

In a step 1330, the receiver node 104 adjusts the step size. Thereceiver node 104 determines the adjustment to the step size based onthe modulation amplitude. In some embodiments, the receiver node 104 maydetermine the step size needed to quantize the signal to the desiredaccuracy, while also not exceeding a given step size to reduceprocessing requirements. The receiver node 104 adjusts the step sizeaccordingly. For example, the receiver node 104 may reduce the stepsize, thereby improving the resolution.

In a step 1340, the receiver node 104 reassesses the modified signal'soutput level. The receiver node 104 may repeat any of the steps 1320,1330, and/or 1340 based on the reassessment, as needed, until thedesired output level is achieved. For example, the receiver node 104 mayiteratively digitize the plurality of signals using the step size,determine the modulation amplitude of the plurality of signals, andadjust the step size based on the modulation amplitude. The step sizemay be set to a smaller amount of time per step to enable determiningsmaller modulation amplitudes, and similarly velocities of nodes withlower velocities (e.g., the aircraft 804).

By utilizing this method, the receiver node 104 can cover the entirerange of Doppler shifts (i.e., from LEO satellites to stationary nodes)without needing a priori knowledge of those shifts for optimumperformance. Doppler-nulling modulation can thus be recovered acrossorders of magnitude Doppler effects. High accuracy can be achievedacross an extremely wide range of possible Doppler effects; from lessthan 1 kHz, for example, to more than 1 MHz.

It is contemplated that the adaptive doppler-nulling digitization may beapplied to both omni and directional systems in order to improveresolution and ultimately the accuracy available from Doppler-nulling.

Referring generally again to FIGS. 1A-13 .

Broadly speaking, doppler bearing (e.g., direction a node is travelingrelative to a null direction) and relative range of a transceiver (Tx)node (e.g., range/distance between the Tx node and a receiver (Rx) node)may be determined using concepts of one or more embodiments of thepresent disclosure.

Generally, doppler shift describes the change in a signal from a Tx nodeto a Rx node (e.g., red shift of light emanating from a star, change infrequency of a sound wave). The doppler shift is a function of themoving vectors between such nodes (e.g., position, velocity,acceleration). Further, over time, the doppler shift will change as afunction of the relative bearing between such nodes.

In some embodiments, Tx nodes and Rx nodes may adjust the phase (e.g.,by changing the phase of a transmitted waveform that is transmitted,and/or by analytically/computationally changing the phase of a receivedwaveform) of a waveform to mimic/cancel the effect of a doppler shift(or theoretical doppler shift). For example, a moving and/or static Txnode may adjust the phase of a signal the Tx node transmits to mimicwhat the phase would look like with a different doppler shift (and/orlack thereof) (e.g., corresponding to a different relative velocity ofthe Tx node). Similarly, for example, a Rx node may adjust (e.g.,computationally adjust) the phase of a signal received from the Tx nodeto cancel out the relative velocity of the Rx node (and/or any otheradjustment). In one example, the Rx node adjusts the phase of a receivedsignal for multiple bearings of the Rx node (over time, as the Rx nodebearing changes). In another example, the Rx node adjusts the phase formultiple bearings of the Tx node. In another example, the Rx nodeadjusts the phase for multiple bearings of the Rx node and for multiplebearings of the Tx node.

In some embodiments, a received signal (e.g., adjusted by the Tx nodebefore sending) is compared to an expected signal (e.g., expectedfunction, signal to noise ratio (SNR), spread spectrum symbol sequence,frequency, amplitude, timing of symbols, timing of pulses, and/or thelike). Such a comparison may be used to acquire/generate a probabilityfunction. For example, multiple of such comparisons (e.g., over time)may be used for different bearings to acquire/generate an expectedbearing. In another example, a single comparison (e.g., as describedabove) may be used by a Rx node to adjust (e.g., digitally) for both theTx node adjustment and the Rx node adjustment to obtain (at least) thebearing of the Tx node.

In some embodiments, a range (i.e., distance) between nodes isdetermined (configured to be determined) based on a time delay between atransmission and a reception between two nodes. For example, a rangebetween nodes may vary as a function of the relative propagation delayof signals between the nodes.

Variations of the embodiments described above may be utilized to achievea variety of benefits. At least some of the nonlimiting variations aredescribed below.

In some embodiments, various relative attributes of one or more Tx nodesmay be determined, generated, and the like by a Rx node based ontransmissions (e.g., signals, communications, RF signals, symbols,phases, and the like) of the one or more Tx nodes. For example, in atleast this context, relative may mean a Tx node relative to a referenceframe, position, bearing, vector, and the like (e.g., the Tx noderelative to the Rx node).

In one example, relative bearing may be determined. In another example,relative range may be determined. In another example, relative positionmay be determined. In another example, relative velocity may bedetermined. In another example, relative acceleration may be determined.For example, in some embodiments, all of the above relative attributesmay be determined from one or more signals.

In at least some embodiments, generally, certain knowledge may be usedby a Rx node (e.g., knowledge that is already known, apriori,standardized, determined dynamically based on a pre-determined and/orascertainable protocol, and/or the like) to determine relativeattributes (e.g., bearing, velocity, range, and the like) of the Txnode. For example, a bearing reference, frequency reference, andprotocol may be used to determine such relative attributes. Note that,in a sense, knowing the protocol may inherently mean knowing the bearingreference and the frequency reference if such information is based onthe protocol. In some examples, a time reference may be used todetermine the relative attributes.

The bearing reference may be referred to as a null direction, nullreference, common null direction, common null direction of a commonreference frame, and the like. The bearing reference may be relative toa specific position (e.g., relative to the north pole in Earth-basedcoordinates, or any arbitrary position). Note that bearing reference maybe static and/or change over time and still be used (e.g., change manytimes per second, with the bearing reference known at each time intervalbased on a commonly known and/or ascertainable protocol).

In at least some embodiments, the frequency reference is based on aprotocol. In one example, the frequency reference may be an expectedreference frequency. In another example, the frequency reference is anascertainable reference frequency. For example, the frequency referencemay be a frequency of symbols within the same bandwidth that aremodulated. In another example, the frequency reference may a frequencyof symbols within aperiodic bandwidths that are modulated. In oneexample, the Tx node signal preamble (without the transmission message)has a frequency equal to the reference frequency. In one example, the Txnode signal message (the message being transmitted) has a frequencyequal to the reference frequency.

In some embodiments, at least the frequency reference is determinedbased on a protocol (e.g., calibration protocol) at the start ofoperations/communications. For example, a static Tx node (referencepoint) in or near an area (e.g., field to be harvested) may be used totransmit to a static Rx node (e.g., tractor, or any other Rx node) toestablish a bias between such nodes (and therefore the frequencyreference may be determined). Next, when the Rx node (tractor) movesover time (relative velocity), any shift in frequency may be known to bepurely a doppler shift (e.g., and used to determine the doppler shift).

In some embodiments, a time reference may be known by the Tx node andknown and/or ascertainable by the Rx node. For instance, the timereference could be plus or minus a few seconds and used to determinewhich portion of a repeated cyclical pattern of a changing frequencyprotocol that a Tx is using. For example, a protocol may be configuredto change the frequency of a signal every 10 seconds to a differentfrequency band. In such an example, in some embodiments, a Rx node mayneed to know which time reference (and corresponding frequency band) asignal is within in order to determine the doppler shift of the signalbecause the doppler shift is based on the expected frequency of thefrequency band. If the wrong frequency band is assumed, the dopplershift could be incorrectly calculated. In some embodiments, to determinerange, time reference may need to be accurate to within a fewmicroseconds or less. For example, the transmission time of a signalhaving a particular speed of transmission through a particular medium(and the time reference of when such a signal was expected to have beensent) may be used, in combination of when such a signal was received byan Rx node, to calculate the time for the distance to travel between theTx node to the Rx node. Such a transmission time can be used along withthe expected speed of transmission (e.g., speed of light, speed of soundin a particular medium, and the like) to determine the range (distance)between the Tx node and the Rx node. Note that similar to the frequencyreference (e.g., using static Tx and Rx nodes during a calibrationprotocol phase of communication) or differently, the time reference maybe capable of being calibrated at the start of a protocol.

Note that protocol, generally, may mean any protocol (e.g.,communication protocol). For example, a protocol may exist to determineand/or vary any attribute (e.g., phase, frequency, time), metric,sequence of events (patterns of signals, etc.), steps, sub-steps,conditional steps, and/or the like of a signal and/or signal recipe overtime. For example, a protocol may be pre-determined to vary a bearingreference (null direction) in 10-degree increments, cyclically. Thebearing reference direction at any given moment in time could depend ona pre-determined routine (e.g., 10°, 190°, 20°, 200°, 30°, 210°, etc.until all 36 directions are rotated through, and then the same or adifferent pattern, over the same or a different range of directions maybe used). In another example, a determinable metric (e.g., time of day,continent, and the like) could be used to dynamically determine thebearing reference pattern (or any other protocol attribute). Forexample, the frequency may be determined by the protocol and dynamicallychange in any way based on the protocol and any other input (e.g.,cyclically change, change based on a received signal, etc.).

Note that the protocol may be based on any known and/or ascertainablerecipe (mechanism, method) such that the Rx may determine the bearingreference (null direction) (e.g., such that the Rx may determine thephase adjustment made by the Tx based on the bearing reference). In someembodiments, time (e.g., time of day) is used to determine the protocol,but the protocol may also be based on other metrics such asPseudo-random number (PN) code, and the like. Ascertainable may meanascertainable by the receiver (e.g., based on the protocol and any otherinformation).

In some embodiments, a protocol may be configured to work based on (orworks better with) certain assumptions holding true. Such assumptionsmay, in some embodiments, help further understand the embodimentsthemselves. Such assumptions may include media propagation assumptions.For example, such media propagation assumptions, if incorrect, mayimpact the accuracy of the determined doppler shift and/or signaltransmissions time. Such assumptions may include having a direct line ofsight between the Tx node and the Rx node and/or having a transmissionwithout impairments (e.g., without multipath and/or reflections).

In some embodiments, different spreads of spectrum (e.g., spectrumbandwidth) of a Tx node signal may be used. For example, differentspreads of spectrum may be used for one or more of the followingpurposes: to determine/ascertain different time references, and/orbearing references; to determine the transmitter (e.g., differenttransmitters may use different spectrum spread); to target differentreceivers (e.g., different receivers may be configured toreceive/analyze only certain spectrum spreads) (e.g., if desire is toadd additional information to a transmission, such as a message); and/orto disclose other information. Such embodiments may use any methods orsystems related to Transmission security (TRANSEC) modes of operationand/or frequency hopped spread spectrum (FHSS) modes of operation.

In some embodiments, but not necessarily all embodiments, a non-zerorelative velocity between a Tx node and a Rx node is required (i.e.,required to exist, but not necessarily known by the Rx node yet) todetermine at least one or more of the relative attributes (e.g., withoutrelative motion, some relative attributes may not be ascertainable usingcertain protocols). For example, where a Tx node and an Rx node aremobile (moving) relative to a reference frame and relative to eachother. In another example, where a Tx node is static and the Rx node ismobile. In another example, where the Tx node is mobile, and the Rx nodeis static.

In some embodiments, a Tx node may be static relative to an Rx node(i.e., zero relative velocity) and some or all relative attributes maystill be ascertainable. For example, a non-Earth reference frame may beused such that the Tx node and Rx node are mobile relative to thenon-Earth reference frame. In some embodiments, an attribute that isascertainable between nodes having zero-relative velocity is that the Rxnode may be able to determine that the Tx node is static relative to theRx node (e.g., lack of doppler shift, the received signal being equal toan expected signal, and the like).

In at least some embodiments, one or more waveform types may be used(e.g., used as the signal wherein a doppler shift (or lack thereof) maybe observed). For example, an electromagnetic waveform may be used(e.g., RF, light, particles such as electrons, neutrons and/or thelike). In another example, a pressure wave is used (e.g., sound wave,seismic wave, vibration wave, and/or the like as a P and/or S wave).

In some embodiments, one or more medium and propagation paths are used(and/or configured to be used). For example, one or more of thefollowing may be used: air medium and electromagnetic waveforms, airmedium and pressure waveforms, water medium and electromagnetic (e.g.,light) waveforms, water medium and pressure waveforms, earth medium andseismic waveforms. Note that any medium and propagation path (orcombinations thereof) may be used. For example, empty space (i.e., lowearth orbit, a vacuum) may be a medium and an electromagnetic waveformmay be used therein.

In some embodiments, a signal to be analyzed for doppler shift that istransmitted by a Tx node to achieve at least some of the benefits of thepresent disclosure (e.g., determining relative attributes) is adjustedin one or more ways. For example, the adjustment to the signal by a Txnode to cancel/mimic doppler shift (as described throughout thisdisclosure) may occur once per transmission (e.g., betweentransmissions) and cycle through bearing reference directions (e.g.,10°, 190°, 20°, 200°, 30°, etc.) as described above without makingfurther adjustments to account for doppler shift. In this regard, thedoppler shift may be adjust for a single direction (perspective). Inanother example, the adjustment to the signal may occur multiple timesper transmission and cycle through bearing reference directions,adjusting the doppler shift before each bearing reference direction. Inthis regard, the doppler shift may be adjusted for each bearingreference direction (all directions). For instance, such adjustmentcould be performed on the preamble of a transmission (e.g., and it maybe part of a protocol to analyze the preamble to obtain the benefits(relative attributes)). In another instance, the adjustment could bedone to the traffic/message (e.g., and likewise the protocol coulddictate that analysis be performed to the traffic/message portion of atransmission). In some embodiments, adjusting the traffic/messageportion for doppler shift results in less/worse SNR (e.g., and may beperformed similar in concept to a blind equalization).

In some embodiments, only a single transmission is used to achievebenefits of the present disclosure (e.g., determining relativeattributes).

In some embodiments, multiple transmissions are used to achieve benefitsof the present disclosure (e.g., determining relative attributes). Forexample, multiple transmissions from the Tx node may be combined toachieve superior results (e.g., more data may make for a more robustdetermination of relative attributes.

Continuing with multiple transmission discussion, a Tx node and Rx nodemay combine info from multiple transmissions in both directions (i.e.,where the Rx node transmits according to the same or differentprotocol), which may result in one or more benefits.

In some embodiments, for example, finer bearing accuracy may be obtainedfrom multiple transmissions. For example, a Tx node may transmit in10-degree increments (e.g., with the null bearing direction in thedirection of transmission) over all 360 degrees. Rx node may receive atleast one of such transmissions (e.g., the transmission in the 10degrees increment that Rx node is located within). Rx node may, based onsuch received transmission, transmit a second transmission over0.5-degree increments in the direction of the received transmission(e.g., over a smaller range of directions such as 30 degrees instead of360 degrees). This pattern may continue in smaller and smallerincrements to a high degree of certainty such that at least one node isaware of the other node's relative bearing (e.g., directionrelative/between each node).

In some embodiments, one or more other benefits may be obtained frommultiple transmissions. For example, higher probability of results maybe obtained. In another example, tracking a moving node may be obtained(e.g., using multiple transmissions over time to). In another example,acceleration may be obtained (e.g., by tracking velocity over time). Inanother example, finer relative timing accuracy may be obtained.

In some embodiments, the protocol is configured to handle a sequence ofsub-protocols (sub-steps) for how to handle multiple transmissionsbetween nodes. For example, the increments used in obtaining finerbearing accuracy as described above may be pre-determined (orascertainable) based upon a known (or ascertainable) protocol.

In some embodiments, multiple transmissions between multiple nodes(e.g., more than two nodes) are utilized and are possible. For example,an Rx node may combine multiple transmissions received from multiplenodes to adapt transmissions (e.g., the Rx node's transmissions). Forinstance, the Rx node may change the spread spectrum to provideinformation such as the reference bearing, number of nodes detected bythe Rx node, and any other information the Rx node may be configured tocommunicate. In another instance, concepts used in graph theory may beutilized to adapt transmissions.

Note that descriptions throughout the present disclosure directed to theTx node may also be applicable to the Rx node in one or moreembodiments. For example, the Rx node may initially receive atransmitted signal from the Tx node but may thereafter (or before)transmit a signal itself according to a protocol and may thereby be atransmitting/transceiver (Tx) node itself. In this regard, descriptionsand figures directed to a Tx node should not be limited to only the Txnode, and may also apply to the Rx node.

In some embodiments, certain aspects of a signal (e.g., the part of thesignal configured to be analyzed per the present disclosure) areanalyzed (e.g., to determine the doppler shift and/or any relativeattribute). The aspects to be analyzed include functions and metrics. Insome examples, the aspects to be analyzed include the SNR and relativevelocity by analyzing the frequency offset (e.g., corresponding to thedoppler shift). In some examples, the aspects to be analyzed include theprotocol for moving through a probability distribution.

In some embodiments, doppler symbol information may be combined withtransmitted information.

In some embodiments, multiple doppler bearing reference exchanges may becombined from multiple nodes to refine relative bearing directionbetween the multiple nodes.

In some embodiments, a temporary bearing reference point with relativepoorly calibrated time reference (e.g., more than a few seconds off) maybe used initially. For example, reference points and measurement pointsmay be placed, and used to synchronize the time reference to highaccuracy between nodes (e.g., to within a couple or single nanosecond).Next, a transmission from a stopped node (e.g., tractor) and other nodesmay be used to eliminate frequency offset biases. The result may be thatthe measurement point (e.g., tractor) can move around (e.g., plow afield) and have accurate time reference and frequency reference to gethighly accurate bearing and range.

A Tx and/or Rx node/system having a controller including one or moreprocessors configured to execute program instructions may cause the oneor more processors to receive a relative position, bearing, and/orvelocity relative of the node relative to a reference bearing, and/orposition; determine an adjusted doppler shift based on such a relativeposition/bearing/velocity; transmit a signal based on the adjusteddoppler shift; and/or the like. In another example, a method includesthe same/similar steps. In another example, DNS is configured to replaceany other positional/navigational system (e.g., GPS, TACAN, radar, etc.)such that position and/or navigation is determined using DNS basedsystems/methods instead (e.g., but other aspects of the systems are leftlargely unchanged). In another example, DNS based systems-methods areused to augment (e.g., increase redundancy, increase accuracy byaveraging results from multiple systems, and the like) existing positionand/or navigation systems/methods. In another example, DNS basedsystems/methods are used to identify nodes (e.g., Tx nodes). In anotherexample, DNS based systems/methods are used to establish communicationlinks by determining a direction of other nodes such that a directionalsignal (e.g., either DNS-based or non-DNS based) may be used with suchnodes.

In some embodiments, increased accuracy is achieved by analyzing signalsfrom multiple (two or more) Tx nodes. For example, conceptually at leastrange and relative bearing (between nodes) is ascertainable usingconcepts herein. If a first Tx node is north and a second Tx node iswest of an Rx node, then the relative range of the first Tx node to theRx node may be combined with the relative bearing (angle) between thesecond Tx node and the Rx node to obtain a more accurate position in theNorth/South direction. Vice versa to determine a more accurate positionin the West/East direction. In this regard, a combination of range andrelative bearing directions may be obtained from a multitude of nodes.Similarly, multiple Rx nodes may be used with a single Tx node to obtaina more accurate position of the Tx node. In another example, multiplenodes in the same or similar or any other direction can be combined,generally, to achieve increased accuracy (e.g., increased confidenceinterval), via any method (e.g., averaging results, median, removingstatistical outliers, and/or any other method for using multiple datapoints of the same type of measurement to increase accuracy).

In some embodiments, DNS or any other concept disclosed herein may beutilized for elevation determination purposes (e.g., altitude, relativeelevation between nodes, etc.). For example, instead of just DNS in 10degree increments laterally, the DNS can be performed in any incrementvertically (e.g., 10-degree increments) and/or laterally. Further, insome embodiments other concepts above may be combined with such ascanning (e.g., finer scanning of 1-degree increments in less than thefull 360 degrees).

In some embodiments, DNS or any other concept disclosed herein may beutilized for determining a position of an entity (e.g., vehicle,non-transmitting object, adversarial target, etc.) using one or morenodes (e.g., a swarm of nodes may detect a node location collectivelyand inform/transmit the position to other nodes of the swarm, such asvia data packets, two-way transmissions, and the like). For example, afirst node may determine the position of the entity (e.g., using anymethod such as radar, imagery, etc.) and, in combination of relativeattributes/positions between at least some of the other nodes (using DNSor any other concept herein) determine the position of the entityrelative to the other nodes (e.g., nodes that did not observe theentity). For example, nodes may know the relative positions to eachother and learn the position of the entity based on only a single nodelearning the position of the entity. Further, for example, any node(e.g., not necessarily the node that determined the entity position) mayknow an absolute position of at least one node. Based on such anabsolute position, the position of the entity (and/or the other nodes)may be determined.

In some embodiments, DNS or any other concept disclosed herein may beutilized for indoor navigation and/or tracking. For example, used forfireman and/or police navigation indoors (e.g., with Tx nodes on eachperson, to track user locations in a building). Since person velocitiesare slower, a more accurate method/system may use ultrasound rather thanRF transmissions to improve accuracies (e.g., due to slow speed ofpropagation).

In some embodiments, DNS or any other concept disclosed herein may beutilized with modified existing protocols (e.g., using othertechniques). For example, protocols of existing systems may be modifiedto be backwards compatible with existing radios but also compatible withradios that use DNS methods. For example, existing preambles may alreadyincorporate some doppler analysis, and modifications to such a protocolcould be made to allow doppler positioning/ranging using DNS methodsdisclosed herein.

In embodiments, even if the Doppler nulling protocol is not known to theRx node 104, the Rx node may observe (e.g., monitor, measure) the netfrequency offset as the Tx node 102 covers (e.g., steers to, orients to,directs antenna elements 112 to) a range of Doppler nulling directions(e.g., relative to the arbitrary direction, each Doppler nullingdirection having a corresponding Doppler nulling angle ϕ). Accordingly,the Rx node 104 may determine the magnitude of the parameter A of thevelocity vector {right arrow over (V′_(T))} of the Tx node 102, to thedegree that the Tx node covers both extremes (e.g., achieves both aminimum and a maximum velocity relative to the Rx node) such that

$A = {\frac{f}{c}{❘\overset{\longrightarrow}{V_{T}^{\prime}}❘}}$

where f is the transmitting frequency of the Tx node and c is the speedof light. For example, each frequency shift point (FSP) detected by theRx node 104 at a given Doppler nulling direction may correspond to avelocity vector of the Tx node 102 relative to the Rx node. As notedabove, and as described in greater detail below, the magnitude parameterA may incorporate a maximum and minimum relative velocity. If, however,the range of Doppler nulling angles ϕ is insufficiently broad, themagnitude parameter A may only include relative maxima and minima forthat limited range of Doppler nulling angles (e.g., as opposed to thefull 360 degrees of possible Doppler nulling angles.

In some embodiments, the Doppler nulling protocol and set of Dopplernulling directions (and corresponding angles ϕ) may be known to the Rxnode 104 and common to all other nodes of the multi-node communicationsnetwork 100. For example, the Tx node 102 may perform the Dopplernulling protocol by pointing a Doppler null in each Doppler nullingdirection and angle ϕ of the set or range of directions as describedabove. The Rx node 104 may monitor the Tx node 102 as the Dopplernulling protocol is performed and may therefore determine, and resolve,the net Doppler frequency shift for each Doppler nulling direction andangle ϕ.

In embodiments, although both the Tx and Rx nodes 102, 104 may be movingrelative to the arbitrary direction, monitoring of the Doppler nullingprotocol by the Rx node 104 may be performed and presented in theinertial reference frame of the Rx node 104 (e.g., in terms of themovement of the Tx node 102 relative to the Rx node 104) to eliminatethe need for additional vector variables corresponding to the Rx node.For example, the velocity vector of the Tx node 102 in a globalreference frame may be shifted according to the velocity vector of theRx node 104, e.g.:

{right arrow over (V′ _(T))}={right arrow over (V _(T))}−{right arrowover (V _(R))}

where {right arrow over (V′_(T))} is the velocity vector of the Tx nodein the inertial reference frame of the Rx node and {right arrow over(V_(T))}, {right arrow over (V_(R))} are respectively the velocityvectors of the Tx node and the Rx node in the Earth reference frame. Inembodiments, either or both of the Tx node 102 and Rx node 104 mayaccordingly compensate for their own velocity vectors relative to theEarth and convert any relevant velocity vectors and relative velocitydistributions into a global reference frame, e.g., for distributionthroughout the multi-node communications network 100. In addition, whilethe representation of the relative motion between the Tx and Rx nodes102, 104 is here presented in two dimensions, the relative motion (and,e.g., any associated velocity vectors, angular directions, Dopplernulling directions, and other parameters) may be presented in threedimensions with the addition of vertical/z-axis components.

In some embodiments, the Rx node 104 may assess and determine Dopplereffects due to the relative motion of the Tx node 102 by measuring timedifferential points (TDP) rather than FSPs. For example, a signaltransmitted at 1 kHz by the Tx node 102 may be subject to 10 Hz ofDoppler frequency shift. This one-percent (1%) change in frequency maybe alternatively expressed as a differential of one percent in the timerequired to measure a cycle of the transmitted signal (or, e.g., anyarbitrary number of cycles). The Doppler effect may be precisely andequivalently characterized in either the frequency domain or the timedomain. For example, graphs which plot the velocity vector of the Txnode 102 relative to the Rx node 104, 104 a-c (y-axis) against theDoppler nulling angle ϕ, may remain consistent between the frequencydomain and the time domain, with the exception that each FSP correspondsto a measured time differential at a given Doppler nulling angle ϕ(e.g., to a TDP) rather than to a measured frequency shift at thatnulling angle.

In some embodiments, due to the nature of the transmitted signal (or,e.g., other conditions) it may be easier or more advantageous for the Rxnode 104 to determine the Doppler shift in the time domain rather thanin the frequency domain. For example, when the signal transmitted by theTx node 102 at a given Doppler nulling direction consists of a series ofshort pulses and a long pulse repetition interval (e.g., as opposed to,e.g., a continuous short-duration pulse), the Rx node 104 may insteaddetermine the Doppler shift to be resolved by measuring the timedifferential between received cycles of the transmitted signal andgenerating time differential profiles based on each determined set ofTDPs. As the resulting time differential profiles plot the relativevelocity vector of the Tx node 102 over a set of Doppler nulling angles4) similarly to the frequency shift profile graphs, the same informationcan be determined by the Rx node 104.

The transmitter node 102 and the receiver node 104 can be timesynchronized to apply Doppler correction respectively for their ownmotions relative to a common inertial reference frame. As a transmitangle advances, a receive angle retreats by a same amount as thetransmit angle advance. This can be understood by first considering atransmitter node 102 when the transmitter node 102 applies full Dopplercorrection in the transmitter node's 102 direction of travel. Next,consider a receiver node 104 directly in line with the path of travelfor the transmitter node 102. If the receiver node 104 at the same timesimilarly applies Doppler correction for the receiver node's 104 motionin line with the transmitter node 102, then at least a near-zero Dopplerpath (e.g., a near-zero Doppler path or a zero Doppler path) will existfrom the transmitter node 102 to the receiver node 104. As shown in FIG.6 , this concept is shown with an arbitrary angle ϕ when both thereceiver node 104 and the transmitter node 102 utilize the samereference frame.

When both the receiver node 104 and the transmitter node apply suchsynchronized Doppler correction relative to the common inertialreference frame, then the Doppler correction can be swept through aplurality of (e.g., some or all) angles so that a zero Doppler path ornear-zero Doppler path will exist from the transmitter node 102 to thereceiver node 104 including the angle resulting in the near-zero Dopplerpath or the zero Doppler path. A zero Doppler path has zero netfrequency offset. For example, an angle resulting in the near-zeroDoppler path may be an angle that is within 5 degrees of the angleresulting in the zero Doppler path. For any combination of thetransmitter node 102 and the receiver node 104 motions and locations,there exists a zero-Doppler path when the Doppler correction angle isequal to the direction angle ϕ. Hence, a zero-Doppler path will beavailable between the transmitter node 102 and the receiver node 104when the two are synchronized to apply Doppler correction for a sweptangle ϕ, relative to the inertial reference, as illustrated in FIG. 6 .Neither the transmitter node 102 nor the receiver node 104 need to knowa direction to the other node in advance.

In some embodiments, the transmitter node 102 may be configured to applythe Doppler corrections relative to the stationary common inertialreference frame for a plurality of (e.g., some or all) azimuthal anglesacross a multi-pulse Doppler group such that each direction along one ofthe plurality of the azimuthal angles has a zero or near-zero Dopplertime interval that would be known to the receiver node based on the timesynchronization. The receiver node 104 may be configured to apply theDoppler corrections relative to the stationary common inertial referenceframe for the plurality of the azimuthal angles across the multi-pulseDoppler group. The receiver node 104 may be configured to apply theDoppler corrections in an inverse fashion as compared to the transmitternode's 102 application of the Doppler corrections. The receiver node 104may be further configured to receive a zero or near-zero Doppler pulsealong a zero or near-zero Doppler path from the transmitter node 102 tothe receiver node 104 with known time intervals. For example, anear-zero Doppler pulse may be a pulse of the multi-pulse Doppler groupthat is closest to a hypothetical zero Doppler pulse.

In some embodiments, the Doppler corrections are in both the frequencydomain and the time domain. In some embodiments, the zero or near-zeroDoppler path is unknown to the transmitter node 102 and the receivernode 104 prior to transmission of the multi-pulse Doppler group. In someembodiments, the receiver node 104 is further configured to coherentlydetect across relatively long correlation sequences (e.g., as comparedto relatively shorter correlation sequences). In some embodiments, withtime corrected pulse-to-pulse, pulse-to-pulse Doppler dispersion isnon-existent. In some embodiments, based at least on the non-existentpulse-to-pulse Doppler dispersion, the receiver node 104 has anincreased sensitivity of signals from the transmitter node 102 ascompared to a sensitivity of signals when the receiver node 104experiences pulse-to-pulse Doppler dispersion. In some embodiments,based at least on the non-existent pulse-to-pulse Doppler dispersion,the receiver node 104 is further configured for deep-noise detection.Deep-noise discovery, as used herein, refers to finding signals soburied under noise that signal power is less than, for example, 1percent of noise power (an equivalent signal-to-noise ratio (SNR) can bestated as −20 decibels (dB)). Employing this technique appears usefulfor very low SNR conditions where signal power levels of 0.1%, 0.01% orless (relative to noise) may be common. In some embodiments, thereceiver node 104 is further configured to correct Doppler time-errorfor subsequent pulses. In some embodiments, the receiver node 104 isfurther configured to additively combine pulse-to-pulse correlationscores to further improve sensitivity of the signals from thetransmitter node 102.

In some embodiments, the stationary common inertial reference frame is atwo-dimensional (2D) stationary common inertial reference frame or athree-dimensional (3D) stationary common inertial reference frame.

In some embodiments, the at least one antenna element 112 of thetransmitter node 102 comprises at least one of at least one directionalantenna element or at least one omnidirectional antenna element. In someembodiments, the at least one antenna element 112 of the receiver node104 comprises at least one of at least one directional antenna elementor at least one omnidirectional antenna element.

It should be noted that the term aircraft, as utilized herein, mayinclude any manned or unmanned object capable of flight. Examples ofaircraft may include, but are not limited to, fixed-wing aerial vehicles(e.g., propeller-powered, jet-powered), rotary-wing aerial vehicles(e.g., helicopters), manned aircraft, unmanned aircraft (e.g., unmannedaerial vehicles, or AUVs), etc. The aircraft may include may include amobile platform such as precision guided equipment, machinery, vehicles,or aircraft including manned (e.g., passenger, cargo, tactical, etc.)and unmanned (e.g., unmanned aerial vehicles (UAVs) or unmanned aircraftsystems (UASs)) aircraft, water, naval, land-based, or other similarvehicles, vessels, or machinery. Additionally, ground-based vehiclesand/or water-based vehicles, as utilized herein, may refer to any typeof vehicles (e.g., manned or unmanned) or other objects capable oftraveling on ground terrain and/or water, respectively.

Although much of the present disclosure is directed to MANETs or othercommunication networks with a mix of mobile and stationary nodesutilizing DNS, this is not intended as a limitation of the presentdisclosure. It is also contemplated that DNS may be used with otherapplications, such as aircraft beacons used to help the aircraft findairports. The DNS may also be used in radar systems. The radar systemsmay utilize transmissions with the DNS protocol. For example, thetransmissions may include time of arrival radar transmissions.

In some embodiments, DNS and DNSA includes adjusting the frequency ofpreambles of special DNS and/or DNSA transmissions to determine relativebearing. Depending upon the duty cycle of Special DNS or DNSAtransmission, these transmissions consume spectrum resources that couldotherwise be used to carry traffic while reducing the duty cycleincreases the amount of time it takes DNS/DNSA to converge. In someembodiments, DNS or DNSA may be performed on wireless traffic insteadof, or in addition to, special DNS/DNSA transmissions. For example, thebody of the transmissions may be used for DNS and/or DNSA instead of, orin addition to, the preambles of the transmission. The DNS over the bodymay reduce the duty cycle needed for special DNS/DNSA transmissions,thus reducing spectrum overhead. DNS over the body may increases thenumber of DNS/DNSA events that are overlaid onto traffic transmissions,thus increasing the number of DNS/DNSA measurements per time thusspeeding up DNS/DNSA convergence. The traffic transmissions may includemobile ad hoc network (MANET) traffic transmissions such as InternetProtocol (IP) packets, MANET control transmissions such as OptimizedLink State Routing (OLSR) protocol packets.

The transmitter nodes 102 may transmit packets and the receiver nodes104 may receive the packets. The packets may be considered wirelesstraffic between the transmitter nodes 102 and the receiver nodes 104. Inembodiments, each of the packets is a fixed-frequency transmission. Itis further contemplated that each of the packets may be afrequency-hopped transmission.

In embodiments, the packets are transmitted and received as radiofrequency (RF) symbols. The receiver node 104 may receive the RF symbolsand convert the RF symbols to digital RF symbols (e.g., by ananalog-to-digital converter (ND converter) in an RF front end of thereceiver node 104). The RF signals may also be down-converted from areceived frequency to a signal at a baseband frequency. The signal atthe baseband frequency may include I/Q signals, in which “I” is theamplitude of the in-phase carrier and “Q” is the amplitude of thequadrature-phase carrier. The I/Q signals may be demodulated to decodethe user traffic. Each of the symbols may include a specific phase,magnitude, and frequency. The phase, magnitude, and frequency of thesymbols may be modulated according to the modulation scheme. Forexample, in-phase (I) and quadrature (Q) may be mapped to a number (n)of symbols corresponding to a bit sequency in a constellation map ordiagram. The number of bits per symbol may include, but is not limitedto, 4, 8, 16, 32, 64, 128, any number of bits per symbols therein, or alarger number of bits per symbol. As may be understood, the number ofbits per symbols may be based, at least in part, on the type ofmodulation scheme by which the signal is transmitted.

In embodiments, the packets are single-carrier modulated. In asingle-carrier modulation mode, all symbols may be contiguous such thateach synchronization burst are spaced in time and can be placed in anyof the free channels by frequency hopping. Although not depicted, it isfurther contemplated that the packets may be multi-carrier modulated. Ina multi-carrier modulation mode, the symbols can be contiguous orseparated in frequency.

The packets include a preamble and a body payload. The packets mayoptionally include a midamble and/or a postamble. Each of the preamble,body payload, midamble, and/or postamble is formed of one or more of thesymbols. In embodiments, the frequency of one or more of the symbols maybe doppler nulled according to the doppler nulling protocol, inaccordance with any of the methods previously described herein. Thesymbols of any of the preamble, body payload, midamble, and/or postamblemay be doppler nulled at separate bearing reference directions.

The transmitter node 102 and receiver node 104 may implement thefrequency-hopped transmission via one or more transmission security(TRANSEC) protocols and/or according to a pseudo-random (PN) pattern tomitigate frequency fading.

The DNS/DNSA protocols may be implemented in newly designed waveforms.In addition to newly design waveforms, legacy waveforms may be modifiedso that unmodified and modified transceivers can continue tointeroperate. During transition from not using DNS to using DNS onlegacy waveforms, the older (unmodified) radio/modems will continue tooperate but suffer a slight degradation due to the DNS doppler shifts.Thus, frequency-hopped receivers may continue to operate using theDNS-updated legacy waveforms in a backwards compatible manner.

In another embodiment, a system may include a controller. In oneembodiment, controller includes one or more processors and memory. Inanother embodiment, the one or more processors may be configured toexecute a set of program instructions stored in memory, wherein the setof program instructions are configured to cause the one or moreprocessors to carry out the steps of the present disclosure.

In one embodiment, the one or more processors may include any one ormore processing elements known in the art. In this sense, the one ormore processors may include any microprocessor-type device configured toexecute software algorithms and/or instructions. In one embodiment, theone or more processors may include a desktop computer, mainframecomputer system, workstation, image computer, parallel processor, orother computer system (e.g., networked computer) configured to execute aprogram configured to operate the system, as described throughout thepresent disclosure. It should be recognized that the steps describedthroughout the present disclosure may be carried out by a singlecomputer system or, alternatively, multiple computer systems.Furthermore, it should be recognized that the steps described throughoutthe present disclosure may be carried out on any one or more of the oneor more processors. In general, the term “processor” may be broadlydefined to encompass any device having one or more processing elements,which execute program instructions from memory. Moreover, differentsubsystems of the system (e.g., controller) may include processor orlogic elements suitable for carrying out at least a portion of the stepsdescribed throughout the present disclosure. Therefore, the abovedescription should not be interpreted as a limitation on the presentdisclosure but merely an illustration.

The memory may include any storage medium known in the art suitable forstoring program instructions executable by the associated one or moreprocessors and the data received. For example, the memory may include anon-transitory memory medium. For instance, the memory may include, butis not limited to, a read-only memory (ROM), a random-access memory(RAM), a magnetic or optical memory device (e.g., disk), a magnetictape, a solid-state drive and the like. In another embodiment, thememory is configured to store data. It is further noted that memory maybe housed in a common controller housing with the one or moreprocessors. In an alternative embodiment, the memory may be locatedremotely with respect to the physical location of the processors,controller, and the like. In another embodiment, the memory maintainsprogram instructions for causing the one or more processors to carry outthe various steps described through the present disclosure.

One skilled in the art will recognize that the herein describedcomponents (e.g., operations), devices, objects, and the discussionaccompanying them are used as examples for the sake of conceptualclarity and that various configuration modifications are contemplated.Consequently, as used herein, the specific exemplars set forth and theaccompanying discussion are intended to be representative of their moregeneral classes. In general, use of any specific exemplar is intended tobe representative of its class, and the non-inclusion of specificcomponents (e.g., operations), devices, and objects should not be takenas limiting.

Those having skill in the art will appreciate that there are variousvehicles by which processes and/or systems and/or other technologiesdescribed herein can be affected (e.g., hardware, software, and/orfirmware), and that the preferred vehicle will vary with the context inwhich the processes and/or systems and/or other technologies aredeployed. For example, if an implementer determines that speed andaccuracy are paramount, the implementer may opt for a mainly hardwareand/or firmware vehicle; alternatively, if flexibility is paramount, theimplementer may opt for a mainly software implementation; or, yet againalternatively, the implementer may opt for some combination of hardware,software, and/or firmware. Hence, there are several possible vehicles bywhich the processes and/or devices and/or other technologies describedherein may be affected, none of which is inherently superior to theother in that any vehicle to be utilized is a choice dependent upon thecontext in which the vehicle will be deployed and the specific concerns(e.g., speed, flexibility, or predictability) of the implementer, any ofwhich may vary.

Transmission of a digital signal using continuous bandpass limitedsignals is also done using any combination of modulation of amplitude,frequency or phase of the sinusoidal carrier wave. The modulatingwaveform may consist of rectangular pulses, and the modulatedparameters, which can be termed symbols, can be switched or keyed fromone discrete value to another, using binary or M-ary amplitude-shiftkeying (ASK), frequency-shift keying (FSK), phase-shift keying (PSK),and the like.

Methods of the present disclosure may be employed in software definedradio (SDR), which employs waveform modulation and demodulation schemesof the kind used in radio data transmission but on a software drivenplatform, including but not limited to Frequency Modulation (FM),Amplitude Modulation (AM), Single Side Band (SSB), Double Side Band(DSB), Vestigial Sideband (VSB), Frequency Shift Keying (FSK), PhaseShift Keying (PSK), Gaussian Minimum Shift Keying (GMSK), QuadratureAmplitude Modulation (QAM), Frequency Hopped Spread Spectrum (FHSS),Direct Sequence Spread Spectrum (DSSS), Orthogonal Frequency DivisionMultiplexing (OFDM) and the like.

Software defined radio (SDR) creates radios that function likecomputers, where the functionality of a radio is defined by softwarethat can be upgraded, rather than by fixed hardware. SDR has beendefined as a radio whose signal processing functionality is defined insoftware; where the waveforms are generated as sampled digital signals,converted from digital to analog via a high-speed Digital-to-AnalogConverter (DAC) and then translated to Radio Frequency (RF) for wirelesspropagation to a receiver. The receiver typically employs an RFsubsystem coupled to a high-speed Analog to Digital Converter (ADC) thatcan capture some or all of the channels of the software radio node. Thereceiver then extracts and demodulates the channel waveform usingsoftware executing on a digital processor.

The previous description is presented to enable one of ordinary skill inthe art to make and use the invention as provided in the context of aparticular application and its requirements. As used herein, directionalterms such as “top,” “bottom,” “over,” “under,” “upper,” “upward,”“lower,” “down,” and “downward” are intended to provide relativepositions for purposes of description, and are not intended to designatean absolute frame of reference. Various modifications to the describedembodiments will be apparent to those with skill in the art, and thegeneral principles defined herein may be applied to other embodiments.Therefore, the present invention is not intended to be limited to theparticular embodiments shown and described, but is to be accorded thewidest scope consistent with the principles and novel features hereindisclosed.

With respect to the use of substantially any plural and/or singularterms herein, those having skill in the art can translate from theplural to the singular and/or from the singular to the plural as isappropriate to the context and/or application. The varioussingular/plural permutations are not expressly set forth herein for sakeof clarity.

All of the methods described herein may include storing results of oneor more steps of the method embodiments in memory. The results mayinclude any of the results described herein and may be stored in anymanner known in the art. The memory may include any memory describedherein or any other suitable storage medium known in the art. After theresults have been stored, the results can be accessed in the memory andused by any of the method or system embodiments described herein,formatted for display to a user, used by another software module,method, or system, and the like. Furthermore, the results may be stored“permanently,” “semi-permanently,” temporarily,” or for some period. Forexample, the memory may be random access memory (RAM), and the resultsmay not necessarily persist indefinitely in the memory.

It is noted herein that the one or more components of system may becommunicatively coupled to the various other components of system in anymanner known in the art. For example, the one or more processors may becommunicatively coupled to each other and other components via awireline connection or wireless connection.

The herein described subject matter sometimes illustrates differentcomponents contained within, or connected with, other components. It isto be understood that such depicted architectures are merely exemplary,and that in fact many other architectures can be implemented whichachieve the same functionality. In a conceptual sense, any arrangementof components to achieve the same functionality is effectively“associated” such that the desired functionality is achieved. Hence, anytwo components herein combined to achieve a particular functionality canbe seen as “associated with” each other such that the desiredfunctionality is achieved, irrespective of architectures or intermedialcomponents. Likewise, any two components so associated can also beviewed as being “connected,” or “coupled,” to each other to achieve thedesired functionality, and any two components capable of being soassociated can also be viewed as being “couplable,” to each other toachieve the desired functionality. Specific examples of couplableinclude but are not limited to physically mateable and/or physicallyinteracting components and/or wirelessly interactable and/or wirelesslyinteracting components and/or logically interacting and/or logicallyinteractable components.

Furthermore, it is to be understood that the invention is defined by theappended claims. It will be understood by those within the art that, ingeneral, terms used herein, and especially in the appended claims (e.g.,bodies of the appended claims) are generally intended as “open” terms(e.g., the term “including” should be interpreted as “including but notlimited to,” the term “having” should be interpreted as “having atleast,” the term “includes” should be interpreted as “includes but isnot limited to,” and the like). It will be further understood by thosewithin the art that if a specific number of an introduced claimrecitation is intended, such an intent will be explicitly recited in theclaim, and in the absence of such recitation no such intent is present.For example, as an aid to understanding, the following appended claimsmay contain usage of the introductory phrases “at least one” and “one ormore” to introduce claim recitations. However, the use of such phrasesshould not be construed to imply that the introduction of a claimrecitation by the indefinite articles “a” or “an” limits any particularclaim containing such introduced claim recitation to inventionscontaining only one such recitation, even when the same claim includesthe introductory phrases “one or more” or “at least one” and indefinitearticles such as “a” or “an” (e.g., “a” and/or “an” should typically beinterpreted to mean “at least one” or “one or more”); the same holdstrue for the use of definite articles used to introduce claimrecitations. In addition, even if a specific number of an introducedclaim recitation is explicitly recited, those skilled in the art willrecognize that such recitation should typically be interpreted to meanat least the recited number (e.g., the bare recitation of “tworecitations,” without other modifiers, typically means at least tworecitations, or two or more recitations). Furthermore, in thoseinstances where a convention analogous to “at least one of A, B, and C,and the like” is used, in general such a construction is intended in thesense one having skill in the art would understand the convention (e.g.,“a system having at least one of A, B, and C” would include but not belimited to systems that have A alone, B alone, C alone, A and Btogether, A and C together, B and C together, and/or A, B, and Ctogether, and the like). In those instances where a convention analogousto “at least one of A, B, or C, and the like” is used, in general such aconstruction is intended in the sense one having skill in the art wouldunderstand the convention (e.g., “a system having at least one of A, B,or C” would include but not be limited to systems that have A alone, Balone, C alone, A and B together, A and C together, B and C together,and/or A, B, and C together, and the like). It will be furtherunderstood by those within the art that virtually any disjunctive wordand/or phrase presenting two or more alternative terms, whether in thedescription, claims, or drawings, should be understood to contemplatethe possibilities of including one of the terms, either of the terms, orboth terms. For example, the phrase “A or B” will be understood toinclude the possibilities of “A” or “B” or “A and B.”

From the above description, it is clear that the inventive conceptsdisclosed herein are well adapted to carry out the objects and to attainthe advantages mentioned herein as well as those inherent in theinventive concepts disclosed herein. While presently preferredembodiments of the inventive concepts disclosed herein have beendescribed for purposes of this disclosure, it will be understood thatnumerous changes may be made which will readily suggest themselves tothose skilled in the art and which are accomplished within the broadscope and coverage of the inventive concepts disclosed and claimedherein.

What is claimed:
 1. A system comprising: a transmitter node and areceiver node, wherein each node of the transmitter node and thereceiver node comprises: a communications interface comprising at leastone antenna element; and a controller operatively coupled to thecommunications interface, the controller including one or moreprocessors, wherein the controller has information of own node velocityand own node orientation; wherein each node of the transmitter node andthe receiver node are time synchronized to apply Doppler correctionsassociated with said node's own motions relative to a stationary commoninertial reference frame; wherein the stationary common inertialreference frame is known to the transmitter node and the receiver nodeprior to the transmitter node transmitting a plurality of signals to thereceiver node and prior to the receiver node receiving the plurality ofsignals from the transmitter node; wherein the receiver node isconfigured to digitize the plurality of signals using a step size,determine a modulation amplitude of the plurality of signals, and adjustthe step size based on the modulation amplitude.
 2. The system of claim1, wherein the modulation amplitude is based on said node's own motionsof the receiver node and the transmitter node.
 3. The system of claim 2,wherein a doppler shift of the plurality of signals is between 1 Hz and10 MHz.
 4. The system of claim 1, wherein the receiver node isconfigured to iteratively digitize the plurality of signals using thestep size, determine the modulation amplitude of the plurality ofsignals, and adjust the step size based on the modulation amplitude. 5.The system of claim 1, wherein one of the receiver node or thetransmitter node is a low-earth orbit satellite.
 6. The system of claim1, wherein the transmitter node is configured to adjust a transmitfrequency according to an own speed and an own velocity direction of thetransmitter node so as to perform a transmitter-side Doppler correction;wherein the receiver node is configured to adjust a receiver frequencyof the receiver node according to the own node velocity and the own nodeorientation so as to perform a receiver-side Doppler correction.
 7. Thesystem of claim 6, wherein an amount of adjustment of the adjustedtransmit frequency is proportional to a transmitter node velocityprojection onto a Doppler null direction, wherein an amount ofadjustment of the adjusted receiver frequency is proportional to areceiver node velocity projection onto the Doppler null direction. 8.The system of claim 7, wherein the receiver node is configured todetermine a relative speed between the transmitter node and the receivernode.
 9. The system of claim 8, wherein the receiver node is configuredto determine a direction that the transmitter node is in motion and avelocity vector of the transmitter node.
 10. The system of claim 1,wherein the stationary common inertial reference frame is atwo-dimensional (2D) stationary common inertial reference frame.
 11. Thesystem of claim 1, wherein the stationary common inertial referenceframe is a three-dimensional (3D) stationary common inertial referenceframe.
 12. The system of claim 1, wherein the at least one antennaelement comprises at least one of at least one directional antennaelement or at least one omnidirectional antenna element.
 13. A receivernode comprising: a communications interface comprising at least oneantenna element; and a controller operatively coupled to thecommunications interface, the controller including one or moreprocessors, wherein the controller has information of own node velocityand own node orientation; wherein the receiver node is time synchronizedwith a transmitter node to apply Doppler corrections associated withsaid node's own motions relative to a stationary common inertialreference frame; wherein the stationary common inertial reference frameis known to the transmitter node and the receiver node prior to thetransmitter node transmitting a plurality of signals to the receivernode and prior to the receiver node receiving the plurality of signalsfrom the transmitter node; wherein the receiver node is configured todigitize the plurality of signals using a step size, determine amodulation amplitude of the plurality of signals, and adjust the stepsize based on the modulation amplitude.
 14. The receiver node of claim13, wherein the modulation amplitude is based on said node's own motionsof the receiver node and the transmitter node.
 15. The receiver node ofclaim 14, wherein a doppler shift of the plurality of signals is between1 Hz and 10 MHz.
 16. The receiver node of claim 13, wherein the receivernode is configured to iteratively digitize the plurality of signalsusing the step size, determine the modulation amplitude of the pluralityof signals, and adjust the step size based on the modulation amplitude.17. The receiver node of claim 13, wherein the transmitter node isconfigured to adjust a transmit frequency according to an own speed andan own velocity direction of the transmitter node so as to perform atransmitter-side Doppler correction; wherein the receiver node isconfigured to adjust a receiver frequency of the receiver node accordingto the own node velocity and the own node orientation so as to perform areceiver-side Doppler correction.
 18. The receiver node of claim 17,wherein an amount of adjustment of the adjusted transmit frequency isproportional to a transmitter node velocity projection onto a Dopplernull direction, wherein an amount of adjustment of the adjusted receiverfrequency is proportional to a receiver node velocity projection ontothe Doppler null direction.
 19. The receiver node of claim 18, whereinthe receiver node is configured to determine a relative speed betweenthe transmitter node and the receiver node.
 20. The receiver node ofclaim 19, wherein the receiver node is configured to determine adirection that the transmitter node is in motion and a velocity vectorof the transmitter node.